From Wikipedia
Warhammer Online: Age of Reckoning (officially abbreviated as WAR) is a massively multiplayer online role-playing game based on Games Workshop's Warhammer Fantasy setting.
This takes place within three different racial pairings: Dwarfs vs. Greenskins, Empire vs. Chaos, and High Elves vs. Dark Elves. Although there are only two races per pairing, players may travel to either of the other two pairings to help fight with their friends and allies. There are four types of RvR combat: Skirmishes (random world encounters), Battlefields (objective-driven battles in RvR-specific areas), Scenarios (instanced, point-based battles against the opposing faction), and Campaigns (invading enemy lands and capital cities). RvR contribution includes both Player vs. Player (PvP) combat and (to a lesser extent) Player vs. Environment (PvE) quests so that you can assist your realm in their victory, regardless of preferred play-style.
All activities in WAR contribute to the campaign, as it is the primary focus of the game. Each of the aforementioned activities generate Victory Points (VP) which measure a realm's progress in capturing a zone. When one realm reaches a designated amount of Victory Points in a particular zone, that zone falls under their control and the war pushes deeper into enemy territory. This back and forth struggle for zone control continues until one side holds two racial pairings, and the attacking side may sack, loot, and pillage the enemy's capital city. The capture of a capital city is the pinnacle objective of the campaign. Once a capital city is taken, the attackers are given a period time to loot the city. When this period expires, the defeated players receive increasing support from NPC guards until they are able to force the attackers out of their city and close the gates. At this point the campaign then begins anew, restarting the cycle.