What are Pets in World of Warcraft?

Pets come in three forms in World of Warcraft: Combat, companion and guardian.  Combat and guardian pets can be controlled by a player whereas companion pets are merely for show.  Death Knights, Druids, Hunters, Priests, Shamans and Warlocks can take advantage of combat pets.  However, mostly Hunters and Warlocks are known for using combat pets with Death Knights using them less in the Unholy specification.  Guardian pets can be called upon by a player to help them out in a difficult combat situation but they do not last very long and they are not under strict control like combat pets.  Vanity pets can be collected, bought and achieved and are summoned to be on display.  You can only have one type of pet active at one time.

Pets often are used in combat situations.  Death Knights, Hunters and Warlocks use pets to increase damage during fights.  They control the pets actions through a separate toolbar and this can come in handy in a variety of situations.  Guardian pets can be used when the going gets tough in a fight and since they do not last very long, players do not have to focus on controlling them and can focus on more important aspects of a given encounter.  Vanity pets are used as a way to show off and serve no purpose other than to show other players what a particular character has earned during their adventures in the game.

Pets can be obtained in a variety of ways.  Combat pets for Hunters can be earned by taming wild beasts while Warlocks must learn how to summon demons.  Hunters can tame certain animals equal or below their own level, and the pets level with them over time.  Guardian pets can come from world drops or events.  Eventually, a Warlock can learn to control a Felguard, the last demon they can control, if they spend enough talent points to do so.  Vanity pets come from a bunch of different sources, such as world drops, rare spawns, fishing, logging in during specific events, questing or even being bought.