Difference between folder-action and snapshot-root-action

May be because I’m not English fluent speaker, but can’t see the difference between folder-action and snapshot-root-action. Both configured commands seem to run (before or after) every snapshot.
What’s the difference?

from document actions

--before-folder-action and --after-folder-action are not inherited and must be set explicitly on target folders, while --before-snapshot-root-action and --after-snapshot-root-action are inherited from their parents and can be set at global, host, user or directory level