Clarify index recovery docs (#91861) (#91923)

Mentions that we only report on recoveries for shard copies that
actually exist in the cluster, so you don't see all historical data if,
e.g., the shard copy relocates elsewhere.

Author: DaveCTurner

docs/reference/indices/recovery.asciidoc

@@ -4,10 +4,9 @@
 <titleabbrev>Index recovery</titleabbrev>
 ++++
 
-
-Returns information about ongoing and completed shard recoveries for one or more
-indices. For data streams, the API returns information for the stream's backing
-indices.
+Returns information about ongoing and completed shard recoveries for one or
+more indices. For data streams, the API returns information for the stream's
+backing indices.
 
 [source,console]
 ----
@@ -33,14 +32,14 @@ index, or alias.
 [[index-recovery-api-desc]]
 ==== {api-description-title}
 
-Use the index recovery API
-to get information about ongoing and completed shard recoveries.
+Use the index recovery API to get information about ongoing and completed shard
+recoveries.
 
 // tag::shard-recovery-desc[]
-Shard recovery is the process
-of syncing a replica shard from a primary shard.
-Upon completion,
-the replica shard is available for search.
+Shard recovery is the process of initializing a shard copy, such as restoring a
+primary shard from a snapshot or syncing a replica shard from a primary shard.
+When a shard recovery completes, the recovered shard is available for search
+and indexing.
 
 Recovery automatically occurs during the following processes:
 
@@ -52,6 +51,14 @@ Recovery automatically occurs during the following processes:
 <<indices-split-index,split>> operation.
 // end::shard-recovery-desc[]
 
+The index recovery API reports information about completed recoveries only for
+shard copies that currently exist in the cluster. It only reports the last
+recovery for each shard copy and does not report historical information about
+earlier recoveries, nor does it report information about the recoveries of
+shard copies that no longer exist. This means that if a shard copy completes a
+recovery and then {es} relocates it onto a different node then the information
+about the original recovery will not be shown in the recovery API.
+
 [[index-recovery-api-path-params]]
 ==== {api-path-parms-title}