[DOCS] Rewrite "What is Elasticsearch?" (Part 1)

docs/reference/intro.asciidoc

@@ -1,42 +1,77 @@
 [[elasticsearch-intro]]
 == What is {es}?
-_**You know, for search (and analysis)**_
-
-{es} is the distributed search and analytics engine at the heart of
-the {stack}. {ls} and {beats} facilitate collecting, aggregating, and
-enriching your data and storing it in {es}. {kib} enables you to
-interactively explore, visualize, and share insights into your data and manage
-and monitor the stack. {es} is where the indexing, search, and analysis
-magic happens.
-
-{es} provides near real-time search and analytics for all types of data. Whether you
-have structured or unstructured text, numerical data, or geospatial data,
-{es} can efficiently store and index it in a way that supports fast searches.
-You can go far beyond simple data retrieval and aggregate information to discover
-trends and patterns in your data. And as your data and query volume grows, the
-distributed nature of {es} enables your deployment to grow seamlessly right
-along with it.
-
-While not _every_ problem is a search problem, {es} offers speed and flexibility
-to handle data in a wide variety of use cases:
-
-* Add a search box to an app or website
-* Store and analyze logs, metrics, and security event data
-* Use machine learning to automatically model the behavior of your data in real
-  time
-* Use {es} as a vector database to create, store, and search vector embeddings
-* Automate business workflows using {es} as a storage engine
-* Manage, integrate, and analyze spatial information using {es} as a geographic
-  information system (GIS)
-* Store and process genetic data using {es} as a bioinformatics research tool
-
-We’re continually amazed by the novel ways people use search. But whether
-your use case is similar to one of these, or you're using {es} to tackle a new
-problem, the way you work with your data, documents, and indices in {es} is
-the same.
+
+https://github.com/elastic/elasticsearch[{es}] is a distributed, RESTful search and analytics engine, scalable data store, and vector database built in Java on top of the Apache Lucene library.
+Use {es} to search, index, store, and analyze data of all shapes and sizes in near real-time.
+
+[TIP]
+====
+{es} has a lot of features. Explore the full list on the https://www.elastic.co/elasticsearch/features[product webpage^].
+====
+
+{es} is the heart of the the <<elasticsearch-intro-elastic-stack,Elastic Stack>> and powers the Elastic https://www.elastic.co/enterprise-search[Search], https://www.elastic.co/observability[Observability] and https://www.elastic.co/security[Security] solutions.
+
+{es} is used for a wide and growing range of use cases. Here are a few examples:
+
+* *Monitor log and event data*. Store and analyze logs, metrics, and security event data for operational insights and SIEM.
+* *Build search applications*. Add search capabilities to apps or websites and build enterprise search engines over your organization's internal data sources.
+* *Vector database*. Store and search vectorized data, create vector embeddings with built-in and third-party NLP models.
+* *Retrieval augmented generation (RAG)*. Use {es} as a retrieval engine to augment Generative AI models.
+* *Application and security monitoring*. Monitor and analyze application performance and security data effectively.
+* *Machine learning*. Use machine learning to automatically model the behavior of your data in real time.
+
+This is just a sample of search, observability, and security use cases enabled by {es}. 
+Refer to our https://www.elastic.co/customers/success-stories[customer success stories] for concrete examples across a range of industry verticals.
+// Link to demos, search labs chatbots
+
+[discrete]
+[[elasticsearch-intro-elastic-stack]]
+.What is the Elastic Stack?
+*******************************
+The Elastic Stack refers to the suite of products enabled by {es}:
+
+* https://www.elastic.co/guide/en/kibana/current/index.html[Kibana]. A UI for visualizing and exploring data in {es}.
+* https://www.elastic.co/guide/en/elasticsearch/client/index.html[Client libraries]. Work with {es} in your preferred programming language.
+* https://www.elastic.co/guide/en/logstash/current/introduction.html[Logstash]. A server-side data processing pipeline for ingesting and transforming data from multiple sources and indexing into {es}.
+* https://www.elastic.co/guide/en/fleet/current/fleet-overview.html[Fleet and Elastic Agent.] Elastic Agents is a single, unified way to add monitoring for logs, metrics, and other types of data to a host. Fleet is a central place to configure and monitor your Elastic Agents.
+* https://www.elastic.co/guide/en/beats/libbeat/current/beats-reference.html[Beats]. Lightweight data shippers for sending data from edge machines to {es}.
+* https://www.elastic.co/guide/en/observability/current/apm.html[APM]. Monitor the performance of your applications.
+* https://www.elastic.co/guide/en/elasticsearch/hadoop/current/float.html[{es} Hadoop]. Use {es} as a Hadoop input/output format.
+
+https://www.elastic.co/guide/en/starting-with-the-elasticsearch-platform-and-its-solutions/current/stack-components.html[Learn more about the Elastic Stack].
+*******************************
+// TODO: Remove once we've moved Stack Overview to a subpage?
+
+[discrete]
+[[elasticsearch-intro-deploy]]
+=== Deployment options
+
+To use {es}, you need a running instance of the {es} service.
+You can deploy {es} in various ways:
+
+* https://elastic.co/guide/en/cloud/current/ec-getting-started.html[*Elastic Cloud*]. {es} is available as part of our hosted Elastic Stack offering, deployed in the cloud with your provider of choice. Sign up for a https://cloud.elastic.co/registration[14 day free trial].
+* https://elastic.co/guide/en/cloud-enterprise/current/Elastic-Cloud-Enterprise-overview.html[*Elastic Cloud Enterprise*]. Deploy Elastic Cloud on public or private clouds, virtual machines, or your own premises.
+* https://elastic.co/guide/en/cloud-on-k8s/current/k8s-overview.html[*Elastic Cloud on Kubernetes*]. Deploy Elastic Cloud on Kubernetes.
+* https://www.elastic.co/docs/current/serverless[*Elastic Cloud Serverless* (technical preview)]. Create serverless projects for autoscaled and fully-managed {es} deployments. Sign up for a https://cloud.elastic.co/serverless-registration[14 day free trial].
+* <<elasticsearch-deployment-options,*Self managed*>>. Install, configure, and run {es} on your own premises.
++
+[TIP]
+====
+If you just want to get started quickly with a minimal local setup, refer to <<run-elasticsearch-locally,Run {es} locally>>.
+====
+
+[discrete]
+[[elasticsearch-next-steps]]
+=== Learn more
+
+* <<getting-started, Quickstart>>. A beginner's guide to deploying your first {es} instance, indexing data, and running queries.
+* https://elastic.co/webinars/getting-started-elasticsearch[Webinar: Introduction to {es}]. Register for our live webinars to learn directly from {es} experts.
+* https://www.elastic.co/search-labs[Elastic Search Labs]. Tutorials and blogs that explore AI-powered search using the latest {es} features.
+** Follow our tutorial https://www.elastic.co/search-labs/tutorials/search-tutorial/welcome[to build a hybrid search solution in Python].
+** Check out the https://github.com/elastic/elasticsearch-labs?tab=readme-ov-file#elasticsearch-examples--apps[`elasticsearch-labs` repository] for a range of Python notebooks and apps for various use cases.
 
 [[documents-indices]]
-=== Data in: documents and indices
+=== Documents and indices
 
 {es} is a distributed document store. Instead of storing information as rows of
 columnar data, {es} stores complex data structures that have been serialized
@@ -65,8 +100,7 @@ behavior makes it easy to index and explore your data--just start
 indexing documents and {es} will detect and map booleans, floating point and
 integer values, dates, and strings to the appropriate {es} data types.
 
-Ultimately, however, you know more about your data and how you want to use it
-than {es} can. You can define rules to control dynamic mapping and explicitly
+You can define rules to control dynamic mapping and explicitly
 define mappings to take full control of how fields are stored and indexed.
 
 Defining your own mappings enables you to:
@@ -88,94 +122,6 @@ The analysis chain that is applied to a full-text field during indexing is also
 used at search time. When you query a full-text field, the query text undergoes
 the same analysis before the terms are looked up in the index.
 
-[[search-analyze]]
-=== Information out: search and analyze
-
-While you can use {es} as a document store and retrieve documents and their
-metadata, the real power comes from being able to easily access the full suite
-of search capabilities built on the Apache Lucene search engine library.
-
-{es} provides a simple, coherent REST API for managing your cluster and indexing
-and searching your data. For testing purposes, you can easily submit requests
-directly from the command line or through the Developer Console in {kib}. From
-your applications, you can use the
-https://www.elastic.co/guide/en/elasticsearch/client/index.html[{es} client]
-for your language of choice: Java, JavaScript, Go, .NET, PHP, Perl, Python
-or Ruby.
-
-[discrete]
-[[search-data]]
-==== Searching your data
-
-The {es} REST APIs support structured queries, full text queries, and complex
-queries that combine the two. Structured queries are
-similar to the types of queries you can construct in SQL. For example, you
-could search the `gender` and `age` fields in your `employee` index and sort the
-matches by the `hire_date` field. Full-text queries find all documents that
-match the query string and return them sorted by _relevance_&mdash;how good a
-match they are for your search terms.
-
-In addition to searching for individual terms, you can perform phrase searches,
-similarity searches, and prefix searches, and get autocomplete suggestions.
-
-Have geospatial or other numerical data that you want to search? {es} indexes
-non-textual data in optimized data structures that support
-high-performance geo and numerical queries.
-
-You can access all of these search capabilities using {es}'s
-comprehensive JSON-style query language (<<query-dsl, Query DSL>>). You can also
-construct <<sql-overview, SQL-style queries>> to search and aggregate data
-natively inside {es}, and JDBC and ODBC drivers enable a broad range of
-third-party applications to interact with {es} via SQL.
-
-[discrete]
-[[analyze-data]]
-==== Analyzing your data
-
-{es} aggregations enable you to build complex summaries of your data and gain
-insight into key metrics, patterns, and trends. Instead of just finding the
-proverbial “needle in a haystack”, aggregations enable you to answer questions
-like:
-
-* How many needles are in the haystack?
-* What is the average length of the needles?
-* What is the median length of the needles, broken down by manufacturer?
-* How many needles were added to the haystack in each of the last six months?
-
-You can also use aggregations to answer more subtle questions, such as:
-
-* What are your most popular needle manufacturers?
-* Are there any unusual or anomalous clumps of needles?
-
-Because aggregations leverage the same data-structures used for search, they are
-also very fast. This enables you to analyze and visualize your data in real time.
-Your reports and dashboards update as your data changes so you can take action
-based on the latest information.
-
-What’s more, aggregations operate alongside search requests. You can search
-documents, filter results, and perform analytics at the same time, on the same
-data, in a single request. And because aggregations are calculated in the
-context of a particular search, you’re not just displaying a count of all
-size 70 needles, you’re displaying a count of the size 70 needles
-that match your users' search criteria--for example, all size 70 _non-stick
-embroidery_ needles.
-
-[discrete]
-[[more-features]]
-===== But wait, there’s more
-
-Want to automate the analysis of your time series data? You can use
-{ml-docs}/ml-ad-overview.html[machine learning] features to create accurate
-baselines of normal behavior in your data and identify anomalous patterns. With
-machine learning, you can detect:
-
-* Anomalies related to temporal deviations in values, counts, or frequencies
-* Statistical rarity
-* Unusual behaviors for a member of a population
-
-And the best part? You can do this without having to specify algorithms, models,
-or other data science-related configurations.
-
 [[scalability]]
 === Scalability and resilience: clusters, nodes, and shards
 ++++
@@ -255,13 +201,9 @@ create secondary clusters to serve read requests in geo-proximity to your users.
 the active leader index and handles all write requests. Indices replicated to
 secondary clusters are read-only followers.
 
-[discrete]
-[[admin]]
-==== Care and feeding
-
 As with any enterprise system, you need tools to secure, manage, and
 monitor your {es} clusters. Security, monitoring, and administrative features
 that are integrated into {es} enable you to use {kibana-ref}/introduction.html[{kib}]
 as a control center for managing a cluster. Features like <<downsampling,
 downsampling>> and <<index-lifecycle-management, index lifecycle management>>
-help you intelligently manage your data over time.
+help you intelligently manage your data over time.

docs/reference/modules/shard-ops.asciidoc

@@ -1,7 +1,7 @@
 [[shard-allocation-relocation-recovery]]
 === Shard allocation, relocation, and recovery
 
-Each <<documents-indices,index>> in Elasticsearch is divided into one or more <<scalability,shards>>. 
+Each index in Elasticsearch is divided into one or more <<scalability,shards>>. 
 Each document in an index belongs to a single shard.
 
 A cluster can contain multiple copies of a shard. Each shard has one distinguished shard copy called the _primary_, and zero or more non-primary copies called _replicas_. The primary shard copy serves as the main entry point for all indexing operations. The operations on the primary shard copy are then forwarded to its replicas.

docs/reference/search/search-your-data/near-real-time.asciidoc

@@ -2,7 +2,7 @@
 
 [[near-real-time]]
 === Near real-time search
-The overview of <<documents-indices,documents and indices>> indicates that when a document is stored in {es}, it is indexed and fully searchable in _near real-time_--within 1 second. What defines near real-time search?
+When a document is stored in {es}, it is indexed and fully searchable in _near real-time_--within 1 second. What defines near real-time search?
 
 Lucene, the Java libraries on which {es} is based, introduced the concept of per-segment search. A _segment_ is similar to an inverted index, but the word _index_ in Lucene means "a collection of segments plus a commit point". After a commit, a new segment is added to the commit point and the buffer is cleared.