1. Description
A pet is any creature that a player can summon or tame, like companions and mounts.
Combat pets are companions that a player can partially control to aid them in battle. The classes most associated with combat pets are the warlock and hunter, although unholy death knights can also get permanent pets, and frost mages as priests can summon temporary pets, those are water elementals and shadowfiends.
Guardian pets are creatures that can be summoned, but cannot be controlled. They react as combat pets do when set to Aggressive and Follow. Death knights, shamans, balance druids, mages and hunters (using snake trap) can all get guardian pets, and items which summon guardian pets can be used by any class.
Companions (also called small pets, non-combat pets, follow pets, or vanity pets) are lesser creatures that only provide aesthetic appeal and do not directly affect combat. Mounts are usually creatures which are rideable.
You may have no more than one combat pet and one companion pet summoned at a time. There is no limit on simultaneous guardian pets; a Blood death knight could potentially have 16 at once (10 Army of the Dead ghouls, one Risen Ghoul, four Bloodworms, one Dancing Rune Weapon).

2. Abilities
Combat pets have their own abilities. Once a pet is summoned, its action bar appears above the player's action bar. All combat pets share six commands; they are Attack, Follow, Stay, Aggressive, Defensive, and Passive.
Each pet can have a maximum of four unique abilities. These abilities are either learnt automatically, or, for Hunter pets, acquire through pet talents.

3. Aggro
All pets, with the exception of non-combat pets, will set their owner in combat when they pull aggro. However, if the owner can break combat through effects like Feign Death or Flask of Petrification, they will remain out of combat until either they or their pet take another aggressive action. This is true even if the owner mounts, which will dismiss the pet and send any attacking mobs into Evade.

2. Guardians
Certain items can temporarily summon a pet that will fight for you until it dies or its time limit expires. Some guardian pets are trinkets; these are usually reusable but limited by a cooldown time. A couple of guardian pets are offhand items, (e.g. Ancient Cornerstone Grimoire and Book of the Dead). One is a sword, Dragon's Call, which summons Emerald Dragon Whelps. Others are usable from your inventory but will either be consumable or have a limited number of uses. Guardian pets can be acquired in the following ways:
- Given as a quest reward for certain quest lines (for example, the Are We There, Yeti? quest sequence from Umi Rumplesnicker in Everlook rewards you with Mechanical Yeti).
- Reputation reward, e.g. the Defender of the Timbermaw trinket that summons a Timbermaw Ancestor requires Exalted reputation with Timbermaw Hold.
- Constructed by an Engineering schematic (e.g. the Gnomish Battle Chicken or Arcanite Dragonling) or Jewelcrafting recipe (e.g. Felsteel Boar or Truesilver Boar).
- Random area drops (e.g. the Glowing Cat Figurine that drops in Darkshore).
An early one that many people see is the Dog Whistle in Scarlet Monastery/Library, which drops off of Houndmaster Loksey, with 3 charges. Unlike Hunter and Warlock pets, there is no way to control a guardian pet other than by summoning it and/or waiting until it dies or its time expires. The pet will defend its owner, attacking whatever its owner attacks or whatever attacks the owner, which can lead to its attacking unintended targets before the party is ready for them. Caution is necessary before using such a pet in an instance. Use one only in confined spaces or areas where all but a few enemies have been killed, or just don't use it.

3. Mounts
Mounts are the basic way to player travel on level 20 you can buy a ground mount which will increase your speed with 60%. On 40 level you will have the ability to buy a 100% movment speed ground mount. On 60 you can get filght mount with 150% speed increase. And on 70 - 280% speed flying mount.
To buy these mounts you need to train a riding skill from riding trainers. When you are high enough level to buy the next mount you will recive an letter in your mail box which writes the location of the trainer and mount seller. You can summon flyght mounts only in Outland and Northrend and to summon in Northrend you need to buy Cold Weather Flying skill which costs 1000 gold. You can learn it on 77 level.