Quivers are a type of ammo bag. They contain stacks of arrows used by bow-wielders and crossbow-wielders (as opposed to ammo pouches, which contain stacks of ammo (shot or bullets) used by gun-wielders). WoW makes no distinction between arrows for bows and arrows for crossbows.
On its icon on the action bar where the quiver is equipped, a quiver will display the total number of the arrows that the quiver holds (the number of shots remaining), up to three digits (999). These do not have to be the same type of arrow, but each slot in the quiver will hold only one kind of arrow. When the number of shots remaining exceeds 1000, the number is not displayed.
When the currently equipped stack of arrows runs out of arrows a quiver will automatically re-equip another stack of the same type of arrow, if one exists in the quiver. This way the player will not have to worry about reloading; simply placing several stacks of the same arrows in the quiver. It is advisable to not mix kinds of arrows in a quiver in order to avoid having shooting occasionally halt, waiting for a manual reload.
Quivers, before patch 3.1, provided a rate of fire bonus, from 10 percent for low level quivers to 15 percent to high level quivers. Since patch 3.1 this has changed. Patch notes "Ammunition: All types of gun and bow ammunition now stack to 1000. All quivers and ammo pouches no longer provide haste. 15% ranged haste is now built into the hunter's Auto Shot."
A quiver primarily is of benefit to a hunter. Any character can buy and equip a quiver in a bag slot. Any character can buy and carry arrows and can use the quiver to store the arrows. Only hunters, rogues, and warriors can use or train to use bows and crossbows which fire arrows. The roles and mechanics of rogues and warriors do not use large quantities of arrows; lacking the hunter's autoshoot capability, manually firing each shot, having no special abilities that require shooting, primarily shooting (or throwing, rather than shooting) to pull a mob and doing the bulk of the damage through melee, often using stealth or a charge rather than shooting to engage an opponent; thus they generally forgo an ammo bag in favor of one or two stacks of ammo in a general purpose bag. So only a hunter has the need for the ability of the quiver to feed a large quantity of arrows to the ammo slot.
Currently available quivers:
|-||6||6,000||4||Hunter Starting Gear|
|-||10||10,000||Quest||15 Vyrin's Revenge, Loch Modan|
|-||12||12,000||Quest||18 The Night Watch, Duskwood|
|50||16||16,000||Drop||Ribbly Screwspigot, Blackrock Depths|
|55||16||16,000||2250 10||Alterac Valley Vendors|
|60||18||18,000||Quest||Epic Hunter quest chain|
|68||18||18,000||10 0 0||Honored: Mag'har|
|68||18||18,000||10 0 0||Honored: Kurenai|
|70||24||24,000||Crafted||Leatherworking (350), Revered: Lower City|
|75||28||28,000||Crafted||Leatherworking (415), Honored: Knights of the Ebon Blade|