You can let someone have add-only rights to your Calendar by setting up a Make a Reservation or Suggest an Event button to your Calendar, as they do not edit any existing Events on your Calendar.
The primary difference between these types of “Self-Book” Templates and the others is whether or not the person adding the Event to your Calendar wants people other than you to be able to see the Events.
For pending upon approval Calendars (such as a staff schedule Calendar where requested shifts are posted after confirmation), you can add a Make a Reservation button that is customized to hold for approval.
For option suggestion Event Calendars (such as one for Events in your local community) you can add a Suggest an Event button and share your Calendar publicly.