Call of duty for prestige mode is a multi-player online mode cod4 that is usually unlockable and it avails itself after reaching level 55. This mode rewards players with an icon which occurs next to their names and it is not usually available for the PC version.
After unlocking all the levels, you can give up everything you have worked for to prestige and show it off to other players. We use it as a way to show how experienced certain players are. You are given an emblem and other cool rewards.