freeradius documentation: Auth-Type

Hi, As someone very new to freeradius, I find that I am struggling with the available documentation. I have problem trying to find explanations on important attributes such as Auth-Type on what it means, what are the valid values etc. Can someone point me to the right place? I know http://www.freeradius.org/rfc/attributes.htm is around but it does not list all attributes, including Auth-Type.