Why, Where and How

Being relative newbies to the caravan world could i please ask some questions regarding rallying.. Firstly why is it done, is it a club within the club ?? Secondly where do you go to rally, how near or far from home do they tend to be ?? And lastly how do you get involved with these rallys. Is there another fee to pay on-top of the CC ?? any help or pointers would be great , thanks in advance  .... :-)