Think of an RSVP event as a simple registration: an invitee arrives to your Splash page, inputs his or her information, and submits. Responses are compiled automatically for you (the event planner) in a simple, easily navigated list.
Ticketed events are identical to RSVP pages, only they integrate a ticket purchase option. This ticket purchase becomes the way an individual RSVPs: the individual arrives to the page, chooses the ticket type he or she wants to purchase, inputs payment information, and submits. Just like with RSVPs, the information is compiled for you (the event planner) in a simple list.
Want to issue tickets but not charge a dime? You can create free RSVP tickets by selecting the "Make this an RSVP ticket" option in the ticket type's settings.
It’s important to note, if you created an RSVP event but later decide you want to sell tickets, you can do that without having to create a new page! Refer here for explanation on how.