A History Save Point is a "snapshot" of an object at a specific point in time. Use the "snapshot" revision to revert the topic from one version of the content to another.
A History Save Point is a combination of a trigger action and a save and prompt action. For example, a revision point is created so the user is prompted to make a comment describing their changes in the History Comments window each time they close an object.
The History Save Points defines if or when, a revision point "snapshot" is created for the object. You'll define the combination of trigger points and save and prompt actions based on how content changes in your library and the requirements you may have to revert the object to an earlier revision.
The default setting for each trigger action is set to (none). Recommended: at a minimum, the Object close (if changed) trigger point is set to Save without comments so that revision points are created for your objects.