docs: Add glossary (fixes #430)

docs/ext/scrobbler.rst

@@ -1,3 +1,5 @@
+.. _ext-scrobbler:
+
 ****************
 Mopidy-Scrobbler
 ****************

docs/glossary.rst

@@ -0,0 +1,37 @@
+********
+Glossary
+********
+
+.. glossary::
+
+    backend
+        A part of Mopidy providing music library, playlist storage and/or
+        playback capability to the :term:`core`. Mopidy have a backend for each
+        music store or music service it supports. See :ref:`backend-api` for
+        details.
+
+    core
+        The part of Mopidy that makes multiple frontends capable of using
+        multiple backends. The core module is also the owner of the
+        :term:`tracklist`. To use the core module, see :ref:`core-api`.
+
+    extension
+        A Python package that can extend Mopidy with on or more
+        :term:`backends <backend>`, :term:`frontends <frontend>`, or GStreamer
+        elements like :term:`mixers <mixer>`. See :ref:`ext` for a list of
+        existing extensions and :ref:`extensiondev` for how to make a new
+        extension.
+
+    frontend
+        A part of Mopidy *using* the :term:`core` API. Existing frontends
+        include the :ref:`MPD server <ext-mpd>`, the :ref:`MPRIS/D-Bus
+        integration <ext-mpris>`, the :ref:`Last.fm scrobbler <ext-scrobbler>`,
+        and the :ref:`HTTP server <ext-http>` with JavaScript API. See
+        :ref:`frontend-api` for details.
+
+    mixer
+        A GStreamer element that controls audio volume.
+
+    tracklist
+        Mopidy's name for the play queue or current playlist. The name is
+        inspired by the MPRIS specification.

docs/index.rst

@@ -71,6 +71,7 @@ Reference
 .. toctree::
     :maxdepth: 2
 
+    glossary
     api/index
     modules/index