In the event invitation process, the event coordinator can add individual constituents by selecting the record or multiple constituents by using a selection. After all the invitees have been added to the event, there is no way to tell how or why they were added. For example, if I load all the trustees into an event, all regents, and a handful of random guests no one will be able to tell why a constituent was invited.  Even as the event coordinator, you won't be able to go back and identify why.