Pathfinder Society scenarios are short, 4-hour adventures for use in Pathfinder Society Organized Play. Though they're designed for Pathfinder Society, they can easily be used for any game that uses the 3.5 or Pathfinder RPG rules.
Season 1 kicked off in August 2009 with the launch of the Pathfinder Roleplaying Game. All Season 1 scenarios use the Pathfinder Roleplaying Game and are immediately ready for use in that rules system. Season 1 ran through July 2010.