docs: Add user guide for *Streams and Private Messages*

templates/zerver/help/index.md

@@ -29,6 +29,7 @@ as a “**realm**”.
 - **[Posting and replying](#posting-and-replying)**
 - **[Mention a Team Member](/help/mention-a-team-member)**
 - **[Message formatting](/help/message-formatting.md)**
+- **[Streams and private messages](/help/streams-and-private-messages.md)**
 - **[Uploading and Sharing Files](/help/uploading_sharing_files)**
 - **[Other common questions](#other-common-questions)**
 - **[Signing out](signing-out.md)**

templates/zerver/help/streams-and-private-messages.md

@@ -0,0 +1,96 @@
+# Streams and private messages
+![Streams and private messages overview](/static/images/help/streams-private-overview.png)
+
+Zulip supports both **private messaging** and group chats via conversation **streams**.
+
+**Streams** are either:
+* **Public** - Public streams are for open discussions. All users can subscribe to public streams and discuss there. Any Zulip user can join any public stream in the realm, and can view the complete message history of any public stream without joining the stream.
+* **Private** - Private streams are for confidential discussions and are only visible to users who've been invited to subscribe to them. Users who are not members of a private stream cannot subscribe to the stream or read or send messages to the stream.
+
+**Private messaging** can either be **one-on-one** or **group** conversations. They can only be seen by users participating in the message.
+
+## Creating a new stream message
+![New stream message](/static/images/help/new-stream-message.png)
+
+To submit a new stream message, first click the **New stream message** button located at the bottom of your screen.
+
+![New stream message](/static/images/help/new-stream.png)
+
+A box similar to the one shown in the previous image will appear.
+
+In the **Stream** field, input the stream name of the message you want your message to be located in. When you begin typing a stream name, autocomplete suggestions will appear.
+
+![Stream does not exist](/static/images/help/stream-none.png)
+
+If you attempt to input a nonexistent stream name, an error message will appear.
+
+Once you have entered your stream name, enter the topic for your message in the **Topic** field. Your topic name can be no longer than 52 characters.
+
+Finally, enter your message in the box labeled **Compose your message here...** or messaging box. You can now send your message to the specified stream under the specified topic.
+
+You can always delete your message by clicking the **x** (![x](/static/images/help/x.png)) icon located at the top-right corner of your messaging box.
+
+## Private messaging
+![New private message](/static/images/help/private-message.png)
+
+To submit a new stream message, first click the **New private message** button located at the bottom of your screen.
+
+![New stream message](/static/images/help/private-box.png)
+
+A box similar to the one shown in the previous image will appear.
+
+In the **one or more people...** field, input the username or email address of the user you want to privately message. When you begin typing an email address or username, autocomplete suggestions will appear.
+
+![Nobody does not exist](/static/images/help/nobody.png)
+
+If you attempt to input a nonexistent username or email address, an error message will appear.
+
+Once you have selected the user you want to message, enter your message in the box labeled **Compose your message here...** or messaging box. You can now privately send your message to the specified user.
+
+You can always delete your message by clicking the **x** (![x](/static/images/help/x.png)) icon located at the top-right corner of your messaging box.
+
+## Other features
+While sending either a stream or private message, several features located below the messaging bn the bottom-left corner can aid you in composing your message.
+
+### Emoji
+
+![Emoji feature](/static/images/help/emoji-box.png)
+
+Clicking the **smiley face** (![smiley face](/static/images/help/smiley-button.png)) icon allows a box to appear featuring Zulip's vast collection of emojis. You can select an emoji to include in your message.
+
+### Attach files
+
+![File upload feature](/static/images/help/uploaded.png)
+
+Clicking the **paper clip** (![paper clip](/static/images/help/paper-clip.png)) icon allows you to select a file from your computer and attach it to your message, uploading it to Zulip to share with your peers.
+
+![File upload feature](/static/images/help/uploading.png)
+
+While the file is uploading, a blue box labeled **Uploading...** will appear, and a link to your file will be included in your message once the file has been uploaded.
+
+### Formatting
+
+![Message formatting modal](/static/images/help/message-formatting-summary.png)
+
+Clicking the **A**  (![A](/static/images/help/formatting.png)) icon will reveal a modal window with a summary of message formatting in Zulip. For more information on message formatting, see our [message formatting guide](/help/message-formatting.md).
+
+### Restore draft
+
+![Restore draft](/static/images/help/restore-draft.png)
+
+If you accidentally delete your message by clicking the **x** (![x](/static/images/help/x.png)) icon in the upper right corner of your messaging box, you can restore your previous message by clicking a blue link labeled **Restore draft**, which appears between the **A** (![A](/static/images/help/formatting.png)) and **eye** (![eye](/static/images/help/eye.png)) icons.
+
+### Preview
+
+![Message preview](/static/images/help/preview.png)
+
+Clicking the **eye** (![eye](/static/images/help/eye.png)) icon will allow you to preview your message. To resume editing your message, click the **pencil and paper** (![pencil and paper](/static/images/help/pencil-paper.png)) icon that has replaced the eye icon.
+
+### Press Enter to send
+![Press enter to send](/static/images/help/press-enter.png)
+
+The **Press Enter to send** checkbox allows you to automatically send your message when you press the enter (or return) key on your keyboard.
+
+![Send button](/static/images/help/send.png)
+
+If the box is unchecked, a green **Send** button will appear. You will have to click on the **Send** button to send your message.