The Voice or Thu'um) are phrases of dragon language, consisting of three separate words of power, that can be used to unleash varied powerful effects.
You can learn a total of 20 dragon shouts in the standard version of Skyrim, but that number can be increased to 27 dragon shouts by installing official add-ons.
The Dawnguard add-on adds three new dragon shouts for players, while Dragonborn adds a total of four new dragon shouts.
To acquire a dragon shout, or to strengthen an existing shout: When you unlock the first word of a dragon shout, you will have access to its most basic version.
Unlocking the shout's second and third words will allow for the use of a more powerful shout that will last longer, deal more damage, or have additional effects.
However, certain shouts will have no effect at all unless all three words have been unlocked and are spoken at once.
Some words of power can be learned only at certain points as you progress through the main questline.
A few others require access to locations that become accessible only during specific faction quests (see the table below).
Most words can be learned at any time by discovering a word wall, which are generally located at dragon lairs or in dungeons.
There are two methods of actively seeking information on their locations, both of which can be used concurrently: Dragon shouts are, in many ways, similar to Magic but their use is not restricted by any stats or skills.
To use a shout, it must first be selected from the Shouts or Favorites menu (only one shout or Power can be selected at a time).
The shout can then be used by pressing the Dragon Shout/Power button.