help: Add private-messages.

templates/zerver/help/include/sidebar_index.md

@@ -53,6 +53,7 @@
 ## People
 * [Check whether someone is on-line](/help/check-whether-someone-is-here-or-away)
 * [View someone's profile](/help/view-someones-profile)
+* [Private messages](/help/private-messages)
 
 ## Streams & topics
 * [About streams and topics](/help/about-streams-and-topics)

templates/zerver/help/pm-mention-alert-notifications.md

@@ -1,7 +1,7 @@
 # PMs, mentions, and alerts
 
-You can configure desktop, mobile, and email notifications for private
-messages, [mentions](/help/mention-a-user-or-group), and
+You can configure desktop, mobile, and email notifications for
+[private messages](/help/private-messages), [mentions](/help/mention-a-user-or-group), and
 [alert words](/help/add-an-alert-word).
 
 {settings_tab|notifications}

templates/zerver/help/private-messages.md

@@ -0,0 +1,41 @@
+# Private messages
+
+**Private messages (PMs)** are one-on-one conversations between you and
+another user. **Group private messages (group PMs)** are small
+discussions with a group of users.
+
+PMs and group PMs work well for one-off conversations. If you find yourself
+frequently conversing with the same person or the same group of people, we
+highly recommend [creating a private stream](/help/create-a-stream) for your
+conversations instead.
+
+Note that group PMs are not the same as [user groups](/help/user-groups) or private
+streams. PMs and group PMs do not have
+[topics](/help/about-streams-and-topics), and do not appear in your list of
+streams.
+
+### Send a (group) private message
+
+{start_tabs}
+
+1. [Open the compose box](/help/open-the-compose-box) by typing `x` or clicking
+   **New private message** at the bottom of the screen.
+
+2. Start typing a user's name, and select the user from the list of
+   suggestions. Repeat as necessary.
+
+3. Compose a message, and click **Send**.
+
+{end_tabs}
+
+### Access a (group) private message
+
+There are several ways to access an existing PM or group PM.
+
+* For recent conversations, click on **Private messages** near
+  the top of the left sidebar.
+* Click on any user or group in the right sidebar.
+* Start typing a user's name in [search](/help/search-for-messages). You'll be
+  able to select PMs or group PMs with that user.
+* Open the compose box, and enter in a (list of) users. Type `Ctr + .` (or
+  `Cmd + .` on a mac) to open that conversation.

templates/zerver/help/start-a-new-topic.md

@@ -19,7 +19,7 @@ start a new topic whenever you're not replying to an existing message.
 Don't worry about picking the perfect topic. The first 2-4 words that come
 to mind are great.
 
-Note that topics are not available for private messages (PMs). If you find
+Note that topics are not available for [private messages (PMs)](/help/private-messages). If you find
 yourself wanting topics in a PM, we recommend
 [creating a private stream](/help/create-a-stream).
 

templates/zerver/help/test-mobile-notifications.md

@@ -3,7 +3,7 @@
 Normally, mobile notifications are only sent if you're idle, which isn't
 ideal for testing.
 
-You can instead have mobile notifications sent for all private messages,
+You can instead have mobile notifications sent for all [private messages](/help/private-messages),
 regardless of whether you're on-line.
 
 {settings_tab|notifications}

templates/zerver/help/user-groups.md

@@ -5,6 +5,11 @@ members at once. When you mention a user group, everyone in the group is
 [notified](/help/pm-mention-alert-notifications) as if they were
 individually mentioned.
 
+Note that user groups are not the same as group private messages. If you're
+trying to send a group of people a message, you'll want to either
+[create a stream](/help/create-a-stream), or send a
+[group private message](/help/private-messages).
+
 ### Create a user group
 
 {start_tabs}