Oh, okay Ebbie.

I could tell them your name, address, phone number, work phone or other phone numbers, possibly your email address, what you have checked out, whether or not you owe for overdues and how much, what items you might have said you've lost or claimed to have returned and not paid for or otherwise settled, various notes about you that the staff might have put in ("Likes to read romance novels" or "One really nasty person" or "Says to let her daughter use her card"), and possibly your date of birth, patron type (resident, nonresident, juvenile, etc. -- not mean, nasty, nice), what items you might have on reserve, if a juvenile what school you go to, and this sort of stuff.

Different libraries collect different info, but this stuff is pretty common to all of them.

I could NOT tell them what items you've checked out and returned in past, nor could I tell them if you had checked out a particular item (unless you had returned it within a few days and no one else had checked it out).

Hope this makes it clearer.