The Undo operation: Cancels any editing, reverting the content to the pre-edited state.
Operations that involve the importing and exporting of files (open/close/merge) will delete the edit history. Once that occurs, be aware that states prior to that action cannot be recovered.
The Redo operation: Reapplies the edits to content previously canceled by the Undo operation, once again putting the content in its post-edited state.
