Realms

World of Warcraft uses server clusters (known as 'realms') to allow players to choose their preferred gameplay type and to allow the game to support as many subscribers as it does. Users may have up to ten characters per realm and up to a maximum of fifty characters per account.[24] There are four types of realms: Normal (also known as PvE or player versus environment), PvP (player versus player), RP (a roleplaying Normal/PvE server) and RP-PvP (roleplaying PvP server). The latter two enforce a set of roleplaying rules - players can be penalized for not roleplaying.[25]
Blizzard posts announcements on the login screen of World of Warcraft and on the official forums about realm status or issues. The status for each realm can also be viewed on their main website.
Player versus Environment (PvE) On the PvE (also known as Normal) realms throughout most of the world the PvP flag may only be enabled by actively turning it on, attacking a PvP-flagged player or NPC, entering a "PvP Territory" (such as a Battleground), entering an "Enemy Territory" (an enemy faction Capital City) or casting a positive spell on a friendly PvP-flagged player or NPC. The PvP flag will be removed after 5 minutes from the last PvP action. If the PvP flag was enabled using the command the player will need to turn it off using the same command and then avoid PvP combat for 5 minutes.
Player versus Player (PvP) On a PvP realm, players are flagged for PvP by default. This flag is only disabled when a character is in a friendly faction city or a zone dedicated to newly created characters. All other zones are considered "contested territory" - players are automatically flagged for PvP upon entering a contested zone. Most players will not need to enter a contested zone until roughly level 20.
On PvP servers, a player is limited to creating characters on one faction. This is in contrast to PvE servers, where a player may create both Horde and Alliance characters.
The PvP servers also feature a more "hands-off" approach to server policies, facilitating the state of open war in these servers. Thus, The in-game GMs will deal with PvP related offenses differently than on the PvE realms, and some player actions are allowed to occur. These actions include, but are not limited to, corpse camping, spawn camping, and other PvP related sections of Blizzard's harassment policy.
Roleplaying (RP) The roleplaying servers use the same ruleset as PvE realms, with the exception that players must act and behave in character, and must follow "naming rules" when they name their character. This means that if players go onto one of these realms, those players act as their characters and anything that is not done in character is then out of character and usually in ((double parentheses)), or preceded by "OOC:" It is also against the rules to be off-topic in all public channels, such as General and Trade.[26] However, it should be noted that this is very rarely enforced (unless brought to a Gamemaster's attention numerous times)[citation needed], and out of character chat is common on RP servers, though usually not in such a blatant manner as on non-RP servers.
Role-playing Player versus Player (RPPvP) The role-playing PvP realms are an extension to the role-playing realms in that they use the PvP ruleset instead of the Normal (PvE) ruleset. Blizzard did not initially have this server type when the game was launched; it was added later, largely due to player request.