Battleground

Battlegrounds are instanced areas used for player versus player combat. Each classic battleground (Warsong Gulch, Arathi Basin and Alterac Valley) has two red instance entrance portals: one for the Alliance, and one for the Horde. Crossing these portals was originally one of the ways to enter the queue for their respective battlegrounds. Now, to enter the queue for any battleground, the player must seek out a Battlemaster, which can be found at the portal or in any capital city, or do so through the Player vs. Player tab. Once inside the instance, the two teams will engage in large-scale PvP, with various objectives determining the winner. Players will earn honor points making PvP rewards available.

If a character goes AFK, he/she will leave the battleground and gain the Deserter debuff. This prevents entry to another battleground for a 15 minute duration. You can report an inactive player by right clicking the player's portrait and selecting "Report AFK". When enough reports are registered, a 60 second debuff will begin to count down. Once the timer is up a new debuff will appear that will prevent the player from gaining any honor or marks while it is on. This debuff can be negated as soon as the player engages in PvP combat. This system is often abused, since a player can have good reasons for not participating in PVP, for example when he is defending.

The two initial Battleground areas, Alterac Valley and Warsong Gulch, went live June 7th, 2005. Arathi Basin was added to the list in Patch 1.7 on September 13th, 2005. A fourth battleground, named Eye of the Storm, was released with the Burning Crusade. A fifth battleground, the Strand of the Ancients, was added in Wrath of the Lich King. The sixth battleground, the Isle of Conquest, was added in Patch 3.2 on August 4th, 2009.

Existing battlegrounds

Warsong Gulch

File:Warsong Gulch Graphic.jpg

WSG loading screen

Factions: Silverwing Sentinels, Warsong Outriders

Alliance Base: Silverwing Hold
Alliance Entrance: Silverwing Grove
Horde Base: Warsong Lumber Mill
Horde Entrance: Mor'shan Base Camp

Levels: 10-19, 20-29, 30-39, 40-49, 50-59, 60-69, 70-79, 80
Combatants: 10 per faction

Arathi Basin

File:Arathi Basin Graphic.jpg

AB loading screen

Factions: The League of Arathor, The Defilers

Alliance Base: Trollbane Hall
Alliance Entrance: Refuge Pointe
Horde Base: Defiler's Den
Horde Entrance: Hammerfall

Levels: 20-29, 30-39, 40-49, 50-59, 60-69, 70-79, 80
Combatants: 15 per faction

Alterac Valley

File:Alterac Valley Graphic.jpg

AV loading screen

Factions: Stormpike Guard, Frostwolf Clan

Alliance Base: Dun Baldar
Alliance Entrance: The Headland
Horde Base: Frostwolf Keep
Horde Entrance: Northeast of Sofera's Naze

Levels: 51-60, 61-70, 71-79, 80
Combatants: 40 per faction

Eye of the Storm

File:Eye of the Storm Graphic.jpg

EotS loading screen

WorldMap-NetherstormArena — EotS in-game map

Requires World of Warcraft: The Burning Crusade.

Factions: No factions are directly associated with the battleground, but members of The Exodar and Silvermoon City appear during its battleground holiday.

Alliance Base: Northern rock
Horde Base: Southern rock
Exterior entrance: There is no exterior entrance to the battleground as in the classic battlegrounds, but the Eye of the Storm is located somewhere in Netherstorm

Levels: 61-69, 70-79, 80
Combatants: 15 per faction

Strand of the Ancients

File:Sota loadingscreen.jpg

SotA loading screen

WorldMap-StrandoftheAncients — SotA in-game map

Requires World of Warcraft: Wrath of the Lich King

Factions: No factions are directly associated with the battleground, but members of The Silver Covenant and The Sunreavers appear during its battleground holiday.

Faction bases: Neither side has a fixed base as teams alternate playing offense by attacking the keep and defense by preventing the attack
Exterior entrance: There is no exterior entrance to the battleground as in the classic battlegrounds, but the Strand is presumably found south of Dragonblight

Levels: 71-79, 80
Combatants: 15 per faction

Isle of Conquest

File:Isle of Conquest Loading.jpg

IoC loading screen

WorldMap-IsleofConquest — IoC in-game map

Requires World of Warcraft: Wrath of the Lich King

Factions: No reputation can be gained while playing in the Isle of Conquest, however the Alliance is represented by members of the Alliance Vanguard and the Horde by members of the the Horde Expedition

Alliance Base: Alliance Keep
Horde Base: Horde Keep
Exterior entrance: There is no exterior entrance to the battleground as in the classic battlegrounds, but the Isle of Conquest is located northwest of Sholazar Basin and west of Icecrown

Levels: 71-79, 80
Combatants: 40 per faction

Future Battlegrounds

Battle for Gilneas

In the next expansion pack, Cataclysm, there will be a new battleground called Battle for Gilneas.

Twin Peaks

In the next expansion pack, Cataclysm, there will be a new battleground called Twin Peaks set in the Twilight Highlands. This battleground will pit the Alliance, with the Wildhammer clan, against the Horde, backed by the Dragonmaw clan.

Canceled Battlegrounds

Azshara Crater

Originally slated to be an Alterac Valley style instance, this battleground was far enough along in development that there were even Horde and Alliance entrances in Azshara. It never saw release, however, and with the zone overhaul in Cataclysm removing the physical location in which it would have existed, its fate seems to have been sealed.

Gurubashi Catacombs

A "deathmatch" style battleground, it was scrapped early in development but the concept eventually turned into Arena PvP.

Notes

If you are the highest level in a bracket and you join the queue for that bracket it is possible to become 1 level higher than the maximum level for that bracket (with the exception of the level 71-80 bracket). This is done by joining the queue then leveling up to the next level. Since you are still in the queue for the bracket that is below your current level you will still enter the battleground of the bracket when you queued.

XP in Battlegrounds

Blizzard stated that XP for playing in the battlegrounds has been added in Patch 3.2.
In order to assist those who choose to keep an alt for the purposes of playing in a specific level of battleground, there is an added option to turn off the ability to gain XP. This ability costs 10G to switch on or off and prevents XP gain in all areas of the game. You can find the NPC to turn on or off XP gains named Experience Eliminator by the Battle Masters as a stealthed NPC. If the switch is on (that is, you are not receiving XP) then you will only be matched against others who also have the switch on; this is because the developers assume that if you don't want XP, you must be twinking.[1]
In Alterac Valley (AV) you can earn XP by killing mobs, however the XP gain is very low if a lot of your faction players are within range. Patch 3.1.3
By glitch or by design, XP awards were increased to move twinks to next bracket quickly, but Call to Honor weekend play still acts as a multiplier of this increased amount, allowing the player to add one level in as little as three wins. Players that know this can use PvP for leveling. Example: Level 42 to level 47 was done on a Sunday in about 5 hours. Incredible XP! :)

Wowpedia