I always thought you should be able to buy tickets on line, and they are sent to you with your DME tickets if your doing that. I’m not sure though so don’t count me on that :).
Advanced check in is where you can basically check in to your resort. You can check in up to 10 days early. During the Online Check-in process you will need to provide the same information you do during in person check-in: Name, room requests, address, phone number, credit card etc.
You will not be able to change your reservation via the Online Check-in Service.
Utilizing Online Check-in will not get your room ready any faster than normal processes.
Hope this helps, for more information check out Disney’s Online Resort Check-in.