What does Andorid auto-sync to google?

[wmscottmc]

I know that google apps data such as gmail and google calendar are synced to google. But if I install my own calendar or todo list app, is this app (and the data) also automatically synced?

I am about to upgrade to a Droid X and would like to control what data I backup to my pc, and what data is synced to the google cloud.

Thanks.