Rules: As short as they can be.

• Basketball is a fast, non-contact sport, usually played indoors on a court
• There are five players from each team on the court at any one time, with up to five substitutes sitting on the side line.
• The game begins with the ball being thrown up by the referee. Two players, standing in the center circle, jump for it and try to tap it to one of their team mates.
• Players pass the ball to one another, or run with the ball while bouncing it on the ground.
  The aim of the game is to throw the ball through the hoop.
• Two points are awarded for each successful throw, except for throws from outside the three point line (3 points), or for penalty free throws (one point).
• No holding, tripping, hitting or pushing is allowed. Referees control the game. If a player commits more than five fouls, they are sent off the court for the remainder of the game.
• The ball is round with a circumference of 75-78 cm, and weighs 600-650 grams.

This is almost all that you need to know.