Can you tell me about a big cam?

hi i have been trying to find out what a big cam is...i know that when you have one the car sounds wicked.. i plan on getting a 1997 grand prix gtp and i was looking at some on youtube and i saw some with a big cam and i want one. so i would like to know if its a ton of work how much to do it your self how much for a shop to do it...and when i say it i mean with all the extras to make it work..i here a xp cam i have no idea what that means. and i know kinda what goes on inside the motor so i don't what to here about stuff having a wider range i want to know how much faster your car will go and how it effects rpms.. were do you buy a big cam and is a (big cam) different from a (cam) or a (hot cam)...if you can think of anything else pleas say so but again i don't want to here about things being lifted higher because that's all i know as of now....thanks and please no *** hole comments i do know a bit about car its just a cam is a big ???? for me.