Quest

Quests are objectives given to the player to complete. Quests have an experience reward, and often modify your karma. In Fallout, Fallout 2, Fallout 3 and Fallout: New Vegas there are usually many different ways to solve quests. The Fallout Tactics equivalents, called missions, and Fallout: Brotherhood of Steel quests are much more linear.

Quest types
There are three different types of quests:
 * Main quests form the main storyline of a game.
 * Optional or side quests, are quests which are entirely up to the player to complete or not and do not prevent achieving the goals of the main storyline, though it may tie in to the story, often significantly.
 * Unmarked or freeform quests are small things to do on the side and do not even appear in your quest log (which in the Fallout games is usually a Pip-Boy variant).