Prestige is totally difrent than say call of duty.
Once you hit LV50, you can accumulate more XP and then hit Prestige mode, which is represented by a Yellow Star next to your PSN name (in the ACRO menu).
And you still keep your credits and charcaters and unlocked abilities.
Prestige mode is just to unlock some extra titles emblems etc. not THAT much of a deal but at least your awesome kill points go to SOME use hehehe