Clarify on_raw_message_edit cached message nature

discord/raw_models.py

@@ -97,7 +97,8 @@ class RawMessageUpdateEvent(_RawReprMixin):
     data: :class:`dict`
         The raw data given by the `gateway <https://discord.com/developers/docs/topics/gateway#message-update>`_
     cached_message: Optional[:class:`Message`]
-        The cached message, if found in the internal message cache.
+        The cached message, if found in the internal message cache. Represents the message before
+        it is modified by the data in :attr:`RawMessageUpdateEvent.data`.
     """
 
     __slots__ = ('message_id', 'channel_id', 'data', 'cached_message')

docs/api.rst

@@ -448,7 +448,10 @@ to handle it, which defaults to print a traceback and ignoring the exception.
     regardless of the state of the internal message cache.
 
     If the message is found in the message cache,
-    it can be accessed via :attr:`RawMessageUpdateEvent.cached_message`
+    it can be accessed via :attr:`RawMessageUpdateEvent.cached_message`. The cached message represents
+    the message before it has been edited. For example, if the content of a message is modified and
+    triggers the :func:`on_raw_message_edit` coroutine, the :attr:`RawMessageUpdateEvent.cached_message`
+    will return a :class:`Message` object that represents the message before the content was modified.
 
     Due to the inherently raw nature of this event, the data parameter coincides with
     the raw data given by the `gateway <https://discord.com/developers/docs/topics/gateway#message-update>`_.