Unlike System Restore, this software takes a "snapshot" of everything on one's drive, including not only one's OS and programs but also any data that one has included on that drive--and it does in a matter of only seconds.
Over the past 3 years, there have been a number of instances that I've regretted "updating" my software--iTunes immediately comes to mind.
Provided one has taken a snapshot before downloading, all one needs to do to roll back (revert) one's drive is to restart while pressing the Home key.