A snapshot is a freeze-frame of your photo at that moment in time. It’s a way to save all of your edit settings at a certain point in case you ever wanted to revert back to them. You can create several snapshots to compare different versions of a photo.
Select an earlier state or the current state of your photo in the History panel. Click the Create button
in the Snapshots panel header or press [N].
Just click the snapshot in the Snapshots panel.
In the Snapshots panel, select the snapshot and click the Delete button
in the panel header, or right click it and choose "Delete".
Right click the snapshot and choose "Rename".
Right click the snapshot and choose "Update".