General World PvP

General world PvP is more the PvP that occurs while you are levelling, as

opposed to the organised PvP of battlegrounds.  It will generally occur when

you are wounded or fighting a mob - this is known as ganking. 

ARENAS

Arenas were added in the Burning Crusade, which added a different and exciting new form of PvP. Arenas take the form 2v2, 3v3, or 5v5 battles, with skirmishes available for practice, or ranked battles to gain points to trade in for rewards.

Getting Points

Thankfully, the arena system is quite different to the honor system.  You won't get rewarded for playing non stop in the arena - you get rewarded for skill, and by winning more games than you lose.  There is a matching system which rewards good play, and beating opponents rated more highly than you will net greater rewards than stomping lower-ranked teams.

When you create your team, you will start off at 1500 rating.  That is the baseline, and to maintain 1500 you need to theoretically win 50% of your games.

The arena rating system means that the difference between the ratings of the two teams fighting will determine how many points are awarded to the winner, and how many the loser recieves.  Two teams on 1500 win/lose around 15 rating per game, but a team in the 1400s getting beaten by a team on 2000+ will only lose 2 rating per game. The que system will attempt to match you against a team in your rating range; failing that, you will be matched against any team. That is why sometimes you will experience a long wait before a game, while other times it will instantly pop.  It all depends on who else is queuing at the time.  

Rating gain is on a curve.  Hovering around 1500 rating will net you 400 arena points each month.  However, once you get higher rating, your point gain will increase exponentially.  2000+ rating will give you close to 1000 points a week, and is a very quick way to get some excellent gear.