Hate, aggro, or threat is a mechanism used in many MMORPG

MMORPG

Massively multiplayer online role-playing game is a genre of role-playing video games in which a very large number of players interact with one another within a virtual game world....

s as well as some RPGs

Role-playing video game

Role-playing video games are a video game genre with origins in pen-and-paper role-playing games such as Dungeons & Dragons, using much of the same terminology, settings and game mechanics. The player in RPGs controls one character, or several adventuring party members, fulfilling one or many quests...

 by which non-playing characters (NPCs; such as mob

Mob (computer gaming)

A mob, mobile or monster is a computer-controlled non-player character in a computer game such as an MMORPG or MUD. Depending on context, all such characters in a game may be considered "mobs", or usage may be limited to hostile NPCs and/or NPCs vulnerable to attack.-Purpose of mobs:Defeating...

s) prioritize which players to attack. Players who generate the most hate (gain the most aggro) on an NPC will be preferentially attacked by that NPC. A game may calculate hate generated (aggro gained) by a player on an NPC based on factors such as:

• Whether the NPC is set to attack players on sight (aggressive).
• The distance between the NPC and the player.
• The relative strength of the player compared to the NPC.
• How much damage has been dealt to the NPC by the player.
• Debuffs and status effect
  Status effect
  In role-playing games, a status effect is a temporary modification to a game character’s original set of stats that usually comes into play when special powers and abilities are used, often during combat. It appears in numerous computer and video games of many genres, most commonly in role-playing...
  
  s inflicted on the NPC by the player.
• Heals and buffs given by the player to other players or NPCs (such as pets) who are attacking the NPC.
• Status effects on the player, such as invincibility, sleep, and death, which make him or her more or less favorable to attack.
• Hate generating or reducing abilities (such as taunts or invisibility) used by the player.
• Time elapsed since the player last generated hate on the NPC.

Hate is usually an undesirable side effect of the player's attack on an enemy, but some characters have powers or skills designed to draw the enemy's attention. Such intentionally hate generating abilities are often available to tank

Tank (computer gaming)

A tank is a style of character in gaming, often associated with a character class. A common convention in real-time strategy games, role-playing games, MMORPGs and MUDs, tanks redirect enemy attacks and/or attention toward themselves in order to protect other characters or units...

s, who can withstand more damage than other players and whose team role is to protect the others by distracting the attackers.

Hate can also be manipulated to deter an NPC from attacking. A player may use a hate reducing ability, may ask another player to generate more hate than himself, may run away or move to a distant position, or may stop generating hate and wait for the NPC to attack someone else. In many games, a player who is defeated or killed has his hate reduced to zero.

In games such as Army of Two

Army of Two

Army of Two is a third person shooter video game developed and published by Electronic Arts. It was released on March 4, 2008 for the Xbox 360 and PlayStation 3 consoles. The game is centered upon two mercenaries fighting through war, political turmoil, and a conspiracy from 1993 to 2009...

, while one player acts as a decoy by gaining aggro (shooting continuously), the other player may use different strategies to take down the opposition focused on the one with aggro (such as sniping the enemy while it heads to the other player).

Hate factors also determine whether aggressive NPCs detect and attack players.