User ID
From Facebook Developers Wiki
(Redirected from Uid)
The user ID is a 64-bit int datatype. If you're storing it in a MySQL database, use the BIGINT datatype.
Any time an FBML tag requires a Facebook user ID, you can use the string loggedinuser or profileowner to substitute the IDs of those users.
If you are using fb:pronoun, you can substitute actor for the user ID so you can more easily aggregate feed stories.
