In The Elder Scrolls V: Skyrim for the PC, PS3, and Xbox 360, one of the new features of the game is called Shouting. Shouts are essentially a Dragon power bestowed to humans by the gods, which you’ll learn more about as you go through the main story.
You can begin to shout near the beginning of the game, during the Whiterun quest line. You start with the Unrelenting Force shout, which is kind of like a powerful gust of wind which will stun your enemies, and can knock down items in the area.
To do a basic shout, you just press RB on the Xbox 360, R2 on the PS3, or Z on the PC. To do the stronger version of a shout (if you have access to it) you just press and hold the corresponding button.
You will unlock more shouts, and more powerful versions of shouts as you progress in the game. Not all shouts are required however, so some will be optional and you’ll have to hunt them down to find them all.