Merge pull request #1485 from jsirois/patch-1

Update pex entry.

Author: chrysle

source/key_projects.rst

@@ -534,11 +534,14 @@ pex
 `GitHub <https://github.com/pantsbuild/pex/>`__ |
 `PyPI <https://pypi.org/project/pex>`__
 
-pex is both a library and tool for generating :file:`.pex` (Python EXecutable)
+Pex is a tool for generating :file:`.pex` (Python EXecutable)
 files, standalone Python environments in the spirit of :ref:`virtualenv`.
-:file:`.pex` files are just carefully constructed zip files with a
-``#!/usr/bin/env python`` and special :file:`__main__.py`, and are designed to
-make deployment of Python applications as simple as ``cp``.
+PEX files are :doc:`zipapps <python:library/zipapp>` that
+make deployment of Python applications as simple as ``cp``. A single PEX
+file can support multiple target platforms and can be created from standard
+:ref:`pip`-resolvable requirements, a lockfile generated with ``pex3 lock ...``
+or even another PEX. PEX files can optionally have tools embedded that support
+turning the PEX file into a standard venv, graphing dependencies and more.
 
 .. _pip-tools: