Let's start with two factions:
The Alliance mainly consists of immature players under 13, so usually it's the over-played faction. There's very little cooperation and everyone seems to be a Night Elf. Players choose this also because its the only "pretty" race. Additionally, Alliance PvP is a guaranteed loss, as every player will run around on their own and shouts out insane commands.
This side is pretty much consisted of 15+ year olds who take this game seriously. Most of these serious Horde players act like they were paid to play it and harp on people in Ventrilo to not use swear words. If you wish to be invisible in PvP, roll a healing class and you will never be attacked by Alliance. This is because killing the healer first is a valid strategy, but since Alliance are stupid, Horde healers are immortal and invisible at the same time.
Warrior- All you do is melee combat things for countless hours of your life, nothing more. No one will accept you to do anything but be a tank, sorry Fury Warriors!
Paladin- The first class available to every player who just bought the game. You can be strong AND heal yourself! You are trapped as a meat shield or healer, so no DPS for you.
Hunter- You capture poor, defenseless animals and make them your slave. It's also the base of every argument on thottbot.com to dictate that every weapon is a "Hunter Weapon".
Priest- The healing person, everybody will expect you to heal, but if you try to DPS then you are hated by anyone who doesnt know anything about other classes.
Mage- Only for making food and water for the Koreans, serves as a dispenser.
Shaman- You will be relied on to FROST SHOCK and drop totems. Totems. Totems. That's it.
Druid- you get to transform into animals and do stuff! too bad every class can do something better then you. Your just used to heal in pvp
Warlock- Like Hunters, but satanic. If you enjoy not needing an ounce of skill, warlockery is for you. Requires being able to hit five buttons, those wacky warlocks!
Rogue- These are the official backstabbing guys of the game, this class is usually played be stupid hyperactive basement dwellers who forgot to take their pills. They are also enormous control freaks who will do anything to complain about their class, even though they are by far the most powerful. 99% of the population of WoW.
and that is all.