There not really random characters; their just added to the storyline.
Chat with our AI personalities
Tank Dempsey ( he is the guy with the white points)he is the american Nikolai Belinski the drunk russian who has blue points Takeo Masaki he is an honorable jappanese soilder he has orange/yellow points Edward Richtofen the crazy german/nazi doctor who invented teleporters,zombies,the ray gun ,monkey bomb, wundewaffe dg-2 and the pack a punch i think he has the green points.
the zombies
It means you can upgrade your guns.
you can't officially "Win" but you can get to as high a level as possible, to achieve a "high score". A good way to do this is to make it to the 'Random box' location and get a good weapon. After you do that move toward the rocket launch area? were the pack a punch machine is and upgrade your good weapon. This will insure many rounds of survival :D have fun killin zombies... haha.
You do in Ascension zombies from the first map pack for black ops.