Purspose of restart ,UserUtteranceReverted and ConversationPaused?

I found this code in Rasa demo project.rasa-demo/actions.py at master · RasaHQ/rasa-demo · GitHub

Could anybody explain the purpose of restart button ,UserUtteranceReverted() and ConversationPaused() in 2 way fall back.?

class ActionDefaultFallback(Action):
def name(self) -> Text:
    return "action_default_fallback"

def run(
    dispatcher: CollectingDispatcher,
    tracker: Tracker,
    domain: Dict[Text, Any],
) -> List["Event"]:

    # Fallback caused by TwoStageFallbackPolicy
    if (
        len(tracker.events) >= 4
        and tracker.events[-4].get("name") == "action_default_ask_affirmation"

        dispatcher.utter_template("utter_restart_with_button", tracker)

        return [SlotSet("feedback_value", "negative"), ConversationPaused()]

    # Fallback caused by Core
        dispatcher.utter_template("utter_default", tracker)
        return [UserUtteranceReverted()]

@erohmensing/@Tanja could you please help me with this?

UserUtteranceReverted() removes the previous user input from the tracker (i.e. it is being reverted). So this would could be used when the previous user intent has been classified incorrectly. So he/she can rephrase it. Not sure about the usage in this particular case.