Board Thread:General Discussion/@comment-43368626-20191101203507/@comment-1038387-20191101204418

Undoing a revision undoes one edit. It reverts the edit window to the previous version, adds an automatic edit summary (which can still be changed) and then you have to save it.

A rollback is an anti-vandalism/anti-spam/generic cleanup tool only given to admins and rollbacks (and content mods?). It allowed you to, with one click, roll back all edits made by the last user. So if they made five edits, it rolls them back all at once. It goes automatic; does not offer the opportunuty to add an explanation. It's useful if you have to undo a lot of edits by a single editor, for example.

Both can be done from Recent Changes, History, Diffs and Contributions.