Much the same as on any app

From the Chatter tab: 

• Click your name or photo to go to your profile page.
• Share what you're working on.
• Post files or links to share with other people.
• View, filter, sort, and add comments to your Chatter feed.
• View your people, group, and record recommendations.
• View your company's trending topics to see the topics that are being discussed right now in Chatter.
• The Trending Topics area on the Chatter tab shows the topics that your coworkers are discussing right now in Chatter. See Force.com's: Viewing Your Company's Trending Topics
• Invite people to join your Chatter network. Invited users can view profiles, post on their feed, and join groups but can't see your Salesforce data or records.

Chatter profiles are personal pages for each person in a Salesforce organization. 

• Profiles include contact information, a photo, an About Me section, a Chatter feed, a list of followers, and a list of people and records being followed.
• View other people's profiles by clicking their name in the People tab, a feed, or on a record detail page.
• From your profile, you can:
• Edit your contact information.
• Add additional information about yourself in the About Me section.
• Update your status in the What are you working on? field.
• Upload or delete a profile photo.
• See who's following you and who you're following.
• If you're not following anyone, click Find people to follow in the Following list to view the People tab and start following people. 
• View your group memberships.
• If you're not in any groups, click Join or create groups in the Groups list to view the Groups tab and join some groups. 
• See your recent updates in your Chatter feed.
• View a single feed update.
• View the topics you use most often.

The People tab displays a list of the users in your organization. 

On the People tab:

• Search for users by typing characters of a first or last name in the search box at the top of the page. The list will automatically filter based on what you type.
• At the top of the list, click a letter to list everyone whose last name begins with that letter.
• Click a person's name or photo to view his or her profile.
• Click Follow to see a person's status updates in the Chatter feed on the Home tab and Chatter tab.
• Click Following to stop seeing a person's status updates in the Chatter feed.
• Invite people to join your Chatter network. Invited users can view profiles, post on their feed, and join groups but can't see your Salesforce data or records.
• View the people that Chatter recommends you follow. Click More in the Recommended People section to view all of your recommendations. If no recommendations appear, then you're already following all the recommended people.

The Groups tab displays a list of Chatter groups in your company.

Chatter groups let you collaborate with specific people. For example, if you're working on a team project, you can create a group for your team to share project-related files and information.

You can join up to 100 groups, and your company can have a total of 10,000 groups.

There are two types of Chatter groups:

• Public: Anyone can see the group's posts, comments, and files, but only members can post, comment, and add files. Anyone can join a public group.
• Private: Only members can see and add posts, comments, and files. People must ask to join or be added by the group's owner or managers.

You can easily upload, store, find, follow, share, and collaborate on files in the cloud using the Files page. This includes files you own or have access to from Chatter,  Content, and files posted to Chatter feeds. All file types, up to 2 GB, are supported, including everything from Microsoft® PowerPoint presentations and Excel spreadsheets, to Adobe® PDFs, image files, audio files, and video files. All files you own and have access to are available to share or attach to posts or comments on Chatter feeds.

Files are automatically added to the Files list when:

• You upload a file.
• You or someone else attaches a file to a Chatter feed or comment. This includes files attached to all public groups, whether you're a member or not, and private groups you're a member of, but not private groups you're not a member of.
• Someone else shares a file privately with you using the Sharing dialog box.
• You upload a file to a Content library.
• Someone else uploads a file to a library you're a member of.
• You or someone else creates a content pack or uploads a Web link in Content. You only see files from content packs and Web links you have access to.

On the Files page:

• See all the files you own or have access to and click a specific filter on the sidebar to see a certain group of files:
• All Files shows all files you own and have access to.
• Recently Viewed shows the most recent files you've viewed.
• MY FILES shows all of the files you own, files shared with you, and files you follow.
• Files I Own shows all the files you own.
• Files Shared with Me shows all files that have been shared with you either by a private share or a public post to your profile.
• Files I Follow shows all the files you're following.
• FILES IN MY GROUPS shows all files you or other people attached to groups you're a member of.
• FILES IN MY LIBRARIES shows all files you and other people uploaded to libraries you're a member of and all files you uploaded to your personal library.
• Search for files using specific filters and by typing terms in the Files search box, or the search box at the top of the page. You can search by file name, description, owner, type, or within the file's text. The search results are filtered based on the terms entered.
• Click Upload a File to upload a private file or upload and share the file with people, groups, or via a file link. You own files you upload.
• Click the Preview icon next to a file. Preview lets you see the file without downloading it.
• Click to follow and receive updates about a file in the Chatter feed. Click next to the file you're following to stop receiving updates about the file.
• Click to download, upload a new version, share with people, groups, or via link, and see sharing settings.
• Click a file name to view the file detail page. You can view detail pages for all files, but you'll only see updates in the Chatter feed for files you follow.
• Click a file owner's name to see his or her profile.

To learn who can perform which actions on a file, see Force.com's documentation: File Sharing Settings and Permissions.