Help:Rollbacks' how-to guide

Any user can remove vandalism from a page, but rollbacks and administrators have a rollback button to make this easier. To revert the edits of one user to the last version by the previous author:

Click rollback on the page history, the user contribution list, or on the diff page. Your revert will be marked as a "minor edit" and given the automatic edit summary Reverted edits by X to last version by Y.