help: Tweak user group documentation.

help/create-user-groups.md

@@ -1,12 +1,27 @@
 # Create user groups
 
-User groups allow you to [mention](/help/mention-a-user-or-group) multiple
-users at once, [notifying](/help/dm-mention-alert-notifications) them about a message. For example, you may choose to create user groups for teams in your organization.
+{!user-groups-intro.md!}
 
 ## How to create a user group
 
 {!how-to-create-a-user-group.md!}
 
+## User group options
+
+There are several parameters you can set while creating a user group, which can
+all be changed later.
+
+* **User group name**: The user group name can be in any language, and can
+  include spaces and other punctuation.
+
+* **User group description** (optional)
+
+* **Who can mention this group?**: Configures who is allowed to
+  [mention this group](/help/mention-a-user-or-group).
+
+* **Choose members**: You can copy the membership from an existing stream or
+  user group, add all users, or enter users one by one.
+
 ## Related articles
 
 * [Setting up your organization](/help/getting-your-organization-started-with-zulip)

help/include/user-groups-intro.md

@@ -0,0 +1,5 @@
+User groups allow you to [mention](/help/mention-a-user-or-group) multiple users
+at once. When you mention a user group, everyone in the group is
+[notified](/help/dm-mention-alert-notifications) as if they were personally
+mentioned. For example, you may choose to create user groups for teams in your
+organization.

help/manage-user-groups.md

@@ -1,25 +1,16 @@
 # Manage user groups
 
+{!user-groups-intro.md!}
+
 ## Create a user group
 
+!!! tip ""
+
+    You can modify the group's name, description, and other settings after it
+    has been created.
+
 {!how-to-create-a-user-group.md!}
 
-## User group options
-
-There are several parameters you can set while creating a user group. All of
-which you can change later.
-
-* **User group name**: The user group name can be in any language, and can
-  include spaces and other punctuation.
-
-* **User group description**: Lets users know what the group is used for.
-
-* **Who can mention this group?**: Configures who is allowed to
-  [mention this group](/help/mention-a-user-or-group).
-
-* **Choose members**: You can copy the membership from an existing stream or
-  user group, add all users, or enter users one by one.
-
 ## Change a user group's name or description
 
 {start_tabs}

help/user-groups.md

@@ -1,15 +1,15 @@
 # User groups
 
-User groups allow you to [mention](/help/mention-a-user-or-group) multiple
-users at once, and add users in bulk to an existing stream or user group.
-When you mention a user group, everyone in the group is
-[notified](/help/dm-mention-alert-notifications) as if they were
-individually mentioned.
+{!user-groups-intro.md!}
 
-Note that user groups are not the same as group direct messages. If you're
-trying to send a message to a group of people, you'll want to either
-[create a stream](/help/create-a-stream), or send a
-[group direct message](/help/direct-messages).
+You can also:
+
+- Add a user group to another user group. This individually adds all the users
+  in the group.
+- Subscribe a user group to a stream. This individually subscribes all the users
+  in the group.
+- Compose a [direct message](/help/direct-messages) to a user group. This
+  automatically puts all the users in the group into the addressee field.
 
 ## Browse and join user groups
 
@@ -48,7 +48,7 @@ trying to send a message to a group of people, you'll want to either
 
 {tab|desktop-web}
 
-1. Click on a user group's mention in a message to open their **group card**.
+1. Click on a user group mention in a message to open the **group card**.
 
 {end_tabs}