What is a cheat code and how do you get it

"Cheat codes are where is you enter a code to unlock something in a game. You can these from friends that have played the game, in magazines, or on websites that are made just for getting cheat codes."
Also i imagine the games companies give cheat codes to magazines so that the magazines can improve their own sales because the players of the game would wish to find out the cheat codes and thus by the magazine. < that is how cheat codes originate; from the game company itself.