Help:Rollback

The rollback feature allows sysops to undo malicious or malformed edits, such as spam or bad coding. Since it undoes everything done by the most recent user, it should be used only with caution.

Normal editing (review the page history, select a useful version, and edit from there) can be used by any non-sysop users to accomplish the same goal, albeit with more clicks and taking a bit more time. The undo feature, visible when comparing two diffs, can also sometimes be used.