Improved verbiage in "What?" section (#615)

* Improved verbiage in "What?" section
* Added a sentence about dpctl.tensor
* added link to specs of runtime classes
* use style in img tag

Co-authored-by: Diptorup Deb <[email protected]>

Author: oleksandr-pavlyk

README.md

@@ -2,14 +2,29 @@
 [![Imports: isort](https://img.shields.io/badge/%20imports-isort-%231674b1?style=flat&labelColor=ef8336)](https://pycqa.github.io/isort/)
 [![Coverage Status](https://coveralls.io/repos/github/IntelPython/dpctl/badge.svg?branch=master)](https://coveralls.io/github/IntelPython/dpctl?branch=master)
 
-What?
-====
+About dpctl
+===========
+
 <img align="left" src="https://spec.oneapi.io/oneapi-logo-white-scaled.jpg" alt="oneAPI logo" />
 
-A lightweight Python package exposing a subset of SYCL functionalities, part of Intel(R) [oneAPI](https://oneapi.io) [Base ToolKit](https://software.intel.com/content/www/us/en/develop/tools/oneapi/base-toolkit.html).
+`dpctl` (data parallel control) is a lightweight [Python package](https://intelpython.github.io/dpctl) exposing a
+subset of the Intel(R) oneAPI DPC++ [runtime classes](https://www.khronos.org/registry/SYCL/specs/sycl-2020/html/sycl-2020.html#_sycl_runtime_classes)
+that is distributed as part of [Intel(R) Distribution for Python*](https://software.intel.com/content/www/us/en/develop/tools/oneapi/components/distribution-for-python.html) and
+is included in Intel(R) [oneAPI](https://oneapi.io) [Base ToolKit](https://software.intel.com/content/www/us/en/develop/tools/oneapi/base-toolkit.html).
+`dpctl` lets Python users query SYCL platforms, discover and represent SYCL devices, and construct SYCL queues to control data-parallel code execution on [Intel(R) XPUs](https://www.intel.com/content/www/us/en/newsroom/news/xpu-vision-oneapi-server-gpu.html) from Python.
+
+`dpctl` features classes representing [SYCL unified shared memory](https://www.khronos.org/registry/SYCL/specs/sycl-2020/html/sycl-2020.html#sec:usm)
+allocations as well as higher-level objects such as [`dpctl.tensor.usm_ndarray`](https://intelpython.github.io/dpctl/latest/docfiles/dpctl.tensor_api.html#module-dpctl.tensor) on top of USM allocations.
+
+`dpctl` assists authors of Python native extensions written in C,
+Cython, or pybind11 to use its `dpctl.SyclQueue` object to indicate the offload
+target as well as objects in `dpctl.memory` and `dpctl.tensor` submodules to
+represent USM allocations that are accessible from within data-parallel code executed
+on the target queue.
 
-`dpctl` [provides](https://intelpython.github.io/dpctl) for discovery and selection of SYCL devices, construction of SYCL queues, as well as working with USM allocations.
-<br /><br />
+`dpctl.tensor` submodule provides an array container representing an array in a
+strided layout on top of a USM allocation. The submodule provides an array-API
+conforming oneAPI DPC++ powered library to manipulate the array container.
 
 Requirements
 ============