A tutorial is the part of a game that teaches you how to play, and usually provides an introduction to both the storyline and the gameplay the player can expect during the game proper.
Tutorials often involve you learning the controls and some basic gameplay mechanics. Some games, such as Banjo-Kazooie, allow the player to skip the tutorial altogether. The Simpsons Hit & Run lets the player disable Bart's tutorial tips (which he actually recommends). The Super Smash Bros. series provides a tutorial video in each installment, viewable by remaining idle at the title screen. Starting with Super Smash Bros. Melee, the player can freely view the tutorial at any time by accessing it in one of the submenus.