Player vs. Player
- Dueling - one vs one combat in a controlled environment.
- Battlegrounds - group vs group combat in a competitive environment.
- Open Combat - whenever a player comes across another player of an opposing faction whose PvP Flag is turned on that player can engage the other in combat. This is different from the other types because this is an uncontrolled environment. Players do not have the ability to choose their opponents. In Battlegrounds you will be fighting people close to your level. In dueling you can choose who you wish to fight. In Open Combat (only seen on PvP servers, in the Arena, and any time your PvP flag is on) players 40 levels higher than you can choose to fight you if they so desire and you cannot decline. 10 players of an opposing faction can gang up on you when you are soloing and you cannot decline. However, if you happen to spot some members of the other faction of a reasonable level, and you're ready for a fight...
- World PvP - As of Patch 1.12, the Eastern Plaguelands and Silithus have special PvP related goals.
Killing players of an opposing faction that is the same level, a higher level, or up to eight levels lower will gain a player Honor. If enough Honor is gained, the player will earn a PvP Rank and access to certain items and areas.
PvP also refers to PvP Realms, which are Realms where Open Combat happens much more often since around level 20 players will be pushed into adventuring in contested territories. By level 30, pretty much all your leveling will be done in contested territories. See PvP Flag for more information, or you can also see the official Realm Types page and PvP Combat page.
Many players who only play on PvE realms will talk about how they do so because they think PvP servers are nothing but non-stop ganking, where it's impossible to do anything but die over and over as you're swarmed by level 60s of the other faction. While this does happen from time to time, it's hardly "all that happens". It is true you're likely to end up in a bit of combat you weren't expecting, but so long as you play on one of the newer servers (you can find out which are the new servers here) combat is usually with players of your level, so long as you don't wander into higher leveled areas.
barrens.chat Avoiding and escaping ganks whilst levelling on a PvP server