The On Schedule event is triggered automatically based on your settings.
You can schedule these triggers for any hour of the day (in your timezone) or for every hour of the day. You will see this in the settings pane.
Please note that the trigger is scheduled at the given time. If you have a lot of triggers running at the same time in the same workspace, there could be a small delay. All triggers are executed in order.
Since there is no context action, there are no variables available for this event. You would need to collect any required data in the event code.