A campaign is a collection of stories weaving into an overreaching narrative. It may be a string of published adventures, a chain of home-brewed material, or an Adventure Path designed to be played as a series. A campaign may or may not have a definitive or predefined end point.
Pathfinder RPG Core Rulebook © 2009, Paizo Publishing, LLC; Author Jason Bulmahn, based on material by Jonathan Tweet, Monte Cook, and Skip Williams.