Snapshots boot to a previous state of your system. By default your system is pre-configured to generate a new snapshot when certain events happen, for example updating your system or installing a new package.
The snapshots are taken regardless of the state your system is in at the time. In your case, it sounds like you have restored the version of Gnome that was broken for you (it was only thirteen hours ago you reported the issue fixed by an update: My Gnome+Wayland+Nvidia Destop will not start after update - #22 by josephmendoza). Any time you have a broken system, just be mindful you probably have some broken snapshots too.
If you would like to test the snapshotting feature, try installing or removing some packages and then roll back. Restoring a broken system after you have already fixed it is…not that useful. 