Here are the things you can do in the sidebar:
- favourite a chat
- disable notifications
- view media and docs posted into the chat
Admins can additionally change the title, chat purpose and icon as well as removing people from the chat and deleting the chat for all users. Admins also hold the power to grant admin rights and to revoke it.
If you can't see the sidebar for the chat you're in, slide it out by clicking on the information button in the top right hand corner of the chat window. You can access the sidebar options on mobile the same way.