The Aim of the Game
Ultimate is a non-contact, self-refereed team sport played with a flying disc.
Two teams of seven players compete on a playing field about the same length as a football field, but narrower. At each end of the playing field there is an end zone. Each team defends one endzone. They score a goal if one of their players catches the disc in the opposite end zone.
The player with the disc is called the thrower. The thrower may not run with the disc. Instead they move the disc by passing to team-mates in any direction.
The defensive team gets possession of the disc if an offensive team’s throw is not caught by a player of the same team. Then the defensive team becomes the offensive team and can try to score in the opposite end zone.
Spirit of the game
Ultimate relies upon a Spirit of the Game that places the responsibility for fair play on every player. There are no referees; the players are solely responsible for following and enforcing the rules, even at World Championship. Competitive play is encouraged, but never at the expense of respect between players, adherence to the rules, and the basic joy of play.
Spirit of the Game is the mindful behaviour practiced by players worldwide prior to, during and after a game. It encompasses attitudes and skills such as good knowledge and application of the rules, fair-mindedness, safe play, and spatial awareness, clear and calm communication, and positive and respectful attitude towards teammates, fans, and opponents, in a mutual effort to protect the basic joy of play.
Here a great video explaining what Ultimate Frisbee is: