Authorization in RADIUS, Authorization in freeradius

Hi everyone, I have a general question regarding Authorization in the RADIUS protocol and how it is implemented in freeradius. What does the RADIUS protocol refer to when it talks about Authorization, does it actually refer to users being probably authorized after being authenticated, using the protocol? Are there RADIUS specific attributes that are for authorization? (not authentication). There are ways of implementing authorization into freeradius, but do those simply overwrite the authentication decision? DIAMETER provides such authorization messeges from my understanding but the RADIUS protocol does not talk about any, is this correct? thank you very much regards George