List of all AD Fields

I applogise for such a basic question but I could not seem to find the answer on my own.

I've been tasked with collecting all of the available fields that AD could possibly use. We have inherited one disgustingly unorganized AD structure and looking to clean it up. My boss said that you can customize AD to pretty ask you whatever fields you want it to since it is essentially like a database. Where can I get a list of out of the box fields in which we can choose from?

We are using Windows Server 2008 R2

Thanks in advanced!

Rich E Rich