COD4 and the multiplayer

Can you guys explain me how the ranking systeme works and what can you get by going level up???

the score you get in each game adds up as experience towards your rank.

you rank up every three levels if i remember correctly..

the level cap is 55. as you rank/level up you unlock guns/perks and challenges (that can be completed to unlock extras for weapons and tons of experience)

then at 55, there's prestige mode, which you have the choice to start from scratch at level 1, but have a cool unique icon next to your name. there are 10 prestige modes total.

hope that helped.