Free Radius Software (GNU)

hi
i have heared that there is a package called freeradius used for authenticating!!!
actually i want to learn more about it but i cant find details on how to use it?

is it based on client server model i.e should i have to install in both client and the server machines ?

i am thinking of using a linux machine as afirewall and installing this or any type of other software used for authentication. i cant afford to install it on every client as they may be many and accessing the server from diffrent machines...

thanks in advance

Radius - GNU Project - Free Software Foundation (FSF)

thanx man