Describe each contrib module in its SGML section title

The original titles only had the module name, which is not very useful
when scanning the list.  By adding a very brief description to each
title, the table of contents becomes friendlier.

Also amend the introduction in the "additional modules" appendix, using
the word "Extension" more extensively.  Nowadays, almost all contrib
modules are extensions, so this is also helpful.

Author: Karl O. Pinc <kop@karlpinc.com>
Reviewed-by: Brar Piening <brar@gmx.de>
Discussion: https://postgr.es/m/20230102180015.372995a9@slate.karlpinc.com

doc/src/sgml/contrib.sgml

@@ -1,27 +1,31 @@
 <!-- doc/src/sgml/contrib.sgml -->
 
 <appendix id="contrib">
- <title>Additional Supplied Modules</title>
+ <title>Additional Supplied Modules and Extensions</title>
 
  <para>
-  This appendix and the next one contain information regarding the modules that
-  can be found in the <literal>contrib</literal> directory of the
+  This appendix and the next one contain information on the
+  optional components
+  found in the <literal>contrib</literal> directory of the
   <productname>PostgreSQL</productname> distribution.
   These include porting tools, analysis utilities,
-  and plug-in features that are not part of the core PostgreSQL system,
-  mainly because they address a limited audience or are too experimental
+  and plug-in features that are not part of the core PostgreSQL system.
+  They are separate mainly
+  because they address a limited audience or are too experimental
   to be part of the main source tree.  This does not preclude their
   usefulness.
  </para>
 
  <para>
-  This appendix covers extensions and other server plug-in modules found in
+  This appendix covers extensions and other server plug-in module
+  libraries found in
   <literal>contrib</literal>.  <xref linkend="contrib-prog"/> covers utility
   programs.
  </para>
 
  <para>
-  When building from the source distribution, these components are not built
+  When building from the source distribution, these optional
+  components are not built
   automatically, unless you build the "world" target
   (see <xref linkend="build"/>).
   You can build and install all of them by running:
@@ -46,41 +50,42 @@
 
  <para>
   If you are using a pre-packaged version of <productname>PostgreSQL</productname>,
-  these modules are typically made available as a separate subpackage,
+  these components are typically made available as a separate subpackage,
   such as <literal>postgresql-contrib</literal>.
  </para>
 
  <para>
-  Many modules supply new user-defined functions, operators, or types.
-  To make use of one of these modules, after you have installed the code
+  Many components supply new user-defined functions, operators, or types,
+  packaged as <firstterm>extensions</firstterm>.
+  To make use of one of these extensions, after you have installed the code
   you need to register the new SQL objects in the database system.
   This is done by executing
   a <xref linkend="sql-createextension"/> command.  In a fresh database,
   you can simply do
 
 <programlisting>
-CREATE EXTENSION <replaceable>module_name</replaceable>;
+CREATE EXTENSION <replaceable>extension_name</replaceable>;
 </programlisting>
 
   This command registers the new SQL objects in the current database only,
-  so you need to run it in each database that you want
-  the module's facilities to be available in.  Alternatively, run it in
+  so you need to run it in every database in which you want
+  the extension's facilities to be available.  Alternatively, run it in
   database <literal>template1</literal> so that the extension will be copied into
   subsequently-created databases by default.
  </para>
 
  <para>
-  For all these modules, <command>CREATE EXTENSION</command> must be run
-  by a database superuser, unless the module is
-  considered <quote>trusted</quote>, in which case it can be run by any
+  For all extensions, the <command>CREATE EXTENSION</command> command must be
+  run by a database superuser, unless the extension is
+  considered <quote>trusted</quote>.  Trusted extensions can be run by any
   user who has <literal>CREATE</literal> privilege on the current
-  database.  Modules that are trusted are identified as such in the
-  sections that follow.  Generally, trusted modules are ones that cannot
+  database.  Extensions that are trusted are identified as such in the
+  sections that follow.  Generally, trusted extensions are ones that cannot
   provide access to outside-the-database functionality.
  </para>
 
  <para>
-  Many modules allow you to install their objects in a schema of your
+  Many extensions allow you to install their objects in a schema of your
   choice.  To do that, add <literal>SCHEMA
   <replaceable>schema_name</replaceable></literal> to the <command>CREATE EXTENSION</command>
   command.  By default, the objects will be placed in your current creation
@@ -88,11 +93,11 @@ CREATE EXTENSION <replaceable>module_name</replaceable>;
  </para>
 
  <para>
-  Note, however, that some of these modules are not <quote>extensions</quote>
+  Note, however, that some of these components are not <quote>extensions</quote>
   in this sense, but are loaded into the server in some other way, for instance
   by way of
   <xref linkend="guc-shared-preload-libraries"/>.  See the documentation of each
-  module for details.
+  component for details.
  </para>
 
  &adminpack;