- The first button is to share editing your document with someone.
- The second button is to see the document activity: who has edited it and saved it, etc.
- The third button is to see comments you or other people have made about the document. Comments are also part of the Review tab.
These buttons are at the right of the screen above the Find tool on the ribbon. They are visible no matter which tab you are on. (Applicable to version 1710 of Microsoft Office 365 subscription).