When you prestige you have a few options. Each prestige gives you a "Prestige Credit" which you can use in a few ways in the "Prestige Store"
You can unlock a special emblem/title banner, or you can get 2 hours of extra weapon XP or 2 hours of in game double xp, or you can get an extra create a class, OR (this is the coolest one imo), you can unlock a primary, secondary, lethal, tactical, or a selection of perks for create a class using your credit. (You permanantly get to keep the item through all of your future prestiges too. So if you like a gun that you unlock late in the leveling process, you can unlock it and use it at level 1 if you use the last option. (It's neat and awesome. Personally I unlocked C4 cause it's amazing)