The Pathfinder Adventure Path is a periodically issued series of large advantures; the line was created by Paizo Publishing when they lost the rights to publish Dragon and, especially, Dungeon.
The concept is based on the Adventure Path series of linked adventures that Paizo had been running for several years in Dungeon magazine. Each volume is sequentially numbered, but not dated. Each adventure contains an in-depth Adventure Path scenario, stats for about a half-dozen new monsters, and several support articles meant to give Game Masters additional material to expand their campaign. The Adventure Path scenarios are available singly or as a subscription. Most narrative arcs within the Adventure Path span six scenarios.