diff --git a/readthedocs/quick-references/events-reference.rst b/readthedocs/quick-references/events-reference.rst
index fe181851..eb83cce2 100644
--- a/readthedocs/quick-references/events-reference.rst
+++ b/readthedocs/quick-references/events-reference.rst
@@ -90,7 +90,8 @@ Full documentation for the `MessageRead
 ChatAction
 ==========
 
-Occurs whenever a user joins or leaves a chat, or a message is pinned.
+Occurs on certain chat actions, such as chat title changes,
+user join or leaves, pinned messages, photo changes, etc.
 
 Full documentation for the `ChatAction
 <telethon.events.chataction.ChatAction>`.
diff --git a/telethon/events/chataction.py b/telethon/events/chataction.py
index 781539f7..a38218ab 100644
--- a/telethon/events/chataction.py
+++ b/telethon/events/chataction.py
@@ -6,7 +6,17 @@ from ..tl import types, functions
 @name_inner_event
 class ChatAction(EventBuilder):
     """
-    Occurs whenever a user joins or leaves a chat, or a message is pinned.
+    Occurs on certain chat actions:
+
+    * Whenever a new chat is created.
+    * Whenever a chat's title or photo is changed or removed.
+    * Whenever a new message is pinned.
+    * Whenever a user joins or is added to the group.
+    * Whenever a user is removed or leaves a group if it has
+      less than 50 members or the removed user was a bot.
+
+    Note that "chat" refers to "small group, megagroup and broadcast
+    channel", whereas "group" refers to "small group and megagroup" only.
     """
     @classmethod
     def build(cls, update, others=None, self_id=None):