CTM can "roll back" your PC to an earlier point in time, like before you accidentally erased that critical PowerPoint file, or before a virus thrashed your system.
If that sounds like Windows' own System Restore feature, it is -- but CTM does more than just protect your Registry and system files: It backs up files, folders, and programs as well. Here's an independent (and, truthfully, rather amateurish) video review that provides more detail and some hands-on feedback:
One thing you didn't see in the video is that CTM makes some DOS-level adjustments upon rebooting. That's not a big deal, but I mention it just so you're not surprised by its installation splash-screen when you restart your PC.
I really admire the simplicity of the software's interface, which consists of just three buttons: Restore System, Take a Snapshot, and Advanced. (I think it'll behoove most users to delve into Advanced and set up scheduled snapshots, which is very simple).
However, the one thing I couldn't immediately figure out is how to determine what files, folders, apps, etc. CTM includes in each snapshot. Also, you can't seem to browse the contents of snapshot -- if you want to recover specific files, you have to enter a file or folder name and run a search.
These aren't deal-breakers, but they do make CTM less useful than a more full-fledged "time machine" backup system like Genie Timeline (which remains a favorite). Of course, it's hard to argue with free, so if you want to add another layer of backup protection to your PC, Comodo Time Machine is definitely worth a look.