Player vs. Player

In World of Warcraft, Player vs. Player (commonly abbreviated PvP) denotes combat between players of any kind such as:

Dueling - One versus one combat in a controlled environment. This cannot be done in cities. However, small towns and the areas immediately outside the entrances to capital cities are very popular for dueling.
Battlegrounds - Horde versus Alliance combat in a competitive environment. Before Patch 3.3.3 they rewarded 'marks' for the appropriate battleground, which were used as a sort of currency to purchase rewards from PvP vendors.
Arena PvP System - Organized on-going tournament that allow for matches that take place in instanced controlled environments between players of the same faction as well as the opposing. Available in 2v2, 3v3 and 5v5 formats. Players create teams and boost their Team Rating to earn [Arena Points] by beating similarly rated teams.
War Games - Custom-made group combat between two groups of either faction. Introduced with Arena Season 9, War Games are unrated, user-initiated practice matches that can occur in any Arena or Battleground. While they do not offer experience, [Honor], achievement progress, or win/loss tracking, they are a popular venue for fun, practice, and recruitment purposes.
Random PvP - Whenever a player character comes across another player character of the opposing faction whose PvP flag is turned on (on PvP realms this flag will switch on whenever you go outside the low-level zones that your faction controls, although it can still be activated in these zones, or Sanctuary areas) that player can attack the other. This was often called "World PvP" before the introduction of zone-specific PvP combat goals, and often still is called by this name.
World PvP
- As of Patch 1.12, the Eastern Plaguelands and Silithus have special PvP related goals.
- In Outland , 4 zones have PvP objectives: Hellfire Peninsula, Zangarmarsh, Terokkar Forest, and Nagrand
PvP Zones
- Wintergrasp is a zone that is fully dedicated to PvP and World PvP.

Honor Points

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 Points. Killing players of too low-level will result in zero honor and is usually considered a form of poor sportsmanship.

As of Patch 2.0.1, players can use [Honor Points] with Battleground Marks of Honor to purchase items in Stormwind City's Champions' Hall or Orgrimmar's Hall of Legends. The available items range from consumables, to gems and trinkets, and to superior and epic armor and weapons.

Also, as of Patch 2.4, players can turn in one [Mark of Honor] from each battleground (4 total; [PvP] Concerted Efforts or [PvP] For Great Honor) to gain extra honor (1238 at level 80). These quests are repeatable.

As of Patch 3.3.3, battleground marks are no longer obtained from completing battlegrounds, instead the amount of honor gained has increased and one can trade in their old marks for 185 honor each.

Arena Points

There are three categories of Arena teams: 2v2, 3v3, and 5v5. Any player can be a member of one or more Arena teams, but only one of each type. For example, you cannot be a member of more than one 2v2 Arena team at any one given time but you may leave your current Arena Team using the /teamquit {2v2, 3v3, 5v5} command before joining a new team.

Arena points are awarded at the end of each week based on your Arena Team's rating. Your Arena Team rating raises or lowers based on the games played by the Arena team. Obviously, winning will boost your team's rating and losing (even if by forfeit due to leaving the arena prematurely, disconnecting and/or not joining a queued game) will lower your team's rating.

You need to play at least 30% of the total arena matches your team participates in for the week to be eligible for being awarded Arena Points at the end of the week. For example, if you played three games but your team played a total of 11 games for the week, you will not receive any Arena Points after the weekly update. Only the highest Arena Points from your 2v2, 3v3, or 5v5 teams will be awarded to you each week. So if you are getting more points from your 3v3 team based on its Arena Team rating, you will receive Arena Points based on your 3v3 team and none from your 2v2 nor 5v5 teams.

Arena matches do not award Honor Points nor PvP tokens of any type.

Arena points can be used to purchase epic items from Meminnie in Blade's Edge Mountains or Leeni "Smiley" Smalls in Area 52 (season 3 items). Vixton Pinchwhistle in Area 52 sells season 2 items.

Additional info for Arena PvP System is also available at the official Arena page and a point estimation tool is available at the WoW Armory Arena Calculator.

PvP Tokens

Main article: PvP Tokens

Killing players in some specific locations in Outland can also give the player PvP Tokens such as [Mark of Honor Hold], [Mark of Thrallmar] and [Halaa Battle Token]. These work similar to Marks of Honor but can be redeemed only at PVP vendors of the faction the token is specific to. For example, only PVP vendors associated with Honor Hold sell PVP items for Marks of Honor Hold.

Generally, PVP tokens offer items which are aimed at players who are below level 70.

PvP Rewards

Main article: PvP Rewards

Prior to release Patch 2.0, players needed to attain a PvP rank or reach a certain reputation with a PvP faction to be able to purchase items from a PvP vendor with gold. Generally, it took much time and effort to obtain the rank and reputation need to purchase the best epic items available and few players were able put forth the massive effort.

After Patch 2.0, this system was replaced with a token system whereby players accumulate Marks of Honor, PvP tokens, and Honor Points to use as currency to buy PvP items from various PvP vendors. Technically these purchasable items are no longer PvP Rewards, per se.

PvP items can be purchased from:

Hall of Legends	Champions' Hall
Brave Stonehide Doris Volanthius First Sergeant Hola'mahi Lady Palanseer Raider Bork Sergeant Kien Sergeant Thunderhorn Stone Guard Zarg	Captain Dirgehammer Captain O'Neal Lieutenant Jackspring Lieutenant Karter Lieutenant Tristia Master Sergeant Biggins Sergeant Major Clate

They can also be purchased from PvP vendors in Zangarmarsh, Hillsbrad Foothills, Ashenvale, Arathi Highlands, and in Halaa of Nagrand.

PvP Realms

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.

Pros and Cons of PvP realms

Pros

Some players like the thrill and risk of random player vs. player combat, and would consider PvE servers to have a difficulty that is too low.
The danger of PvP inserts more realism into gameplay, since preventing other players from attacking you represents more a pure game mechanic than any plausible scenario.
Opportunities for world PvP are much more prevalent.
If you dislike Alliance-favored population imbalance, research has shown that the population of PvE realms are much more prone to be Alliance weighted, with population ratios often hovering around 2:1. PvP realms are more often horde dominated, with ratios of between 1.5:1 and 3:1 being most common, and 15:1 happening on occasion see WarcraftRealms for more details.

Cons

Some players consider being able to play with no risk of random player vs. player combat less stressful. You can level and train skills without the types of interruptions listed below.
Such disruptive practices like corpse camping, griefing, ganking can be exceedingly prevalent on PvP realms, many high level players may repeatedly and incessantly engage in these behaviors for no obvious reason other than that they can.
Blizzard has shown extreme reluctance to address PvP realm faction balance, and as a result, almost all realms are out of balance to some extent, with horde players outnumbering alliance players in most cases. The WarcraftRealms census says that overall for PvP realms, there are 1.7 horde online for every alliance online. The result of this is that the dominant faction can often so completely dominate a questing / PvP or resource gathering area that the smaller faction has no access.
Priests with [Mind Control], shamans with [Thunderstorm], druids with [Typhoon] and mages with [Blast Wave] can knockback you off cliffs and boats. Sometimes, in rare cases, [Death Grip] can pull players to their doom.