What data does my work's Exchange server store from my Droid?

Hi! I recently was asked to set up my Droid 2 so it would get office email. Under the “Messaging” app I added an account, then put in all of my current “webmail” data. Also checking the boxes for “Calendar, Contacts and Email.” I get it that all that data comes down TO my phone, but what does Exchange take back FROM my phone? Will all of my Gmail and Facebook contacts end up in Exchange? What about my Gmail emails and calendar. Needless to say, some things I would like to keep away from the corporate servers. Is there stuff taken that I wouldn’t know about? Apps? Browser records?