A totem is the primary tool used by a Shaman as an instrument of war. Characterized by their immobility and area of effect, the totems embody the Shaman's mastery over the elements. Some totems possess destructive power while others aid and assist allies. Shamanistic cultures outside those of the Horde and Draenei also possess the ability use totems in battle.
Totems are unique to the Shaman, and must be obtained by completing certain quests. A Shaman can use one totem of each element at any one time: Earth (Nature-based spells), Fire (Fire-based spells), Water (Water/Frost-based spells) and Air (Nature-based spells). Once a totem is put down it cannot be moved, but a new totem can be used to replace it. In other words, the Shaman player can activate a spell that uses the Earth totem, another spell that uses the Fire totem, a third spell that uses the Water totem, and a fourth spell that uses the Air totem at the same time; however, the player cannot activate two spells that use the same totem because the last spell will override the previous one. Although the Shaman's totems are summoned and fixed near the caster, a Shaman player can place a totem while moving. A totem's effect is only active within a certain radius of the totem (making it a hybrid version of Point Blank Area of Effect and Ground Targeted Area of Effect). The totem can be planted underwater, and appears floating at the foot level of the character. Totems are immune to AoEs, and must be specifically attacked to be destroyed.
In order to cast any totem spell, the Shaman must be carrying around a Earth Totem, Fire Totem, Water Totem, or Air Totem as appropriate for the totem spell they wish to cast. Shamans must complete a quest to receive each totem. These quests have several steps and usually require travel to a variety of places. After receiving a totem, the Shaman will be able to cast all totem spells for the corresponding element. The Shaman must keep the totem in a bag with them at all times in order to cast the totem spells for that totem type. The only exception to this is if the Shaman has a relic totem that has the "Counts as an Air, Earth, Fire, and Water Totem" comment (such as Totem of Lightning and Totem of Healing Rains) equipped or in their bag.
In Wrath of the Lich King
As of patch 3.3 each of the horde races have unique totem artwork. 
The first totem received by the Shaman. It allows the Shaman to use totems which do things like enhance defense/offense, slow enemies, and taunt them.
The second totem received in the Shaman's development. This totem is primarily used to deal damage.
The third totem received in the Shaman's development. This totem is used for restoration-type effects.
While not technically a totem, the Enamored Water Spirit trinket is able to summon an improved form of the Mana Spring Totem for a short time.
The final totem received in the Shaman's development. Like the Earth Totem counterpart, it allows totems to enhance certain defensive/offensive aspects. Note: The Horde Air Totem quest doesn't seem to be complete, so the NPC in Thousand Needles just gives it to you. It's not a bug.
- ^ http://www.worldofraids.com/news/169.html
- ^ http://www.wow.com/2009/10/02/patch-3-3-ptr-new-totems-for-trolls/