Quidditch is a mix of rugby, handball and dodgeball. The sport is played worldwide with over 40 teams in both UK and US. It's a gendermixed sport, where everyone is taken into consideration and included. The general rule about gender is that you're only allowed to have a maximum of four players of one gender on pitch at all times.
A game of quidditch is played between two teams. The goal is to end the game with more points than the opposing team. A roster can have up to 21 players for a quidditch match, but only 1 Keeper, 3 Chasers, 2 Beaters, 1 Seeker may be on-pitch at any given time.
CHASERS AND KEEPERS
On pitch during gameplay you're only allowed to have a maximum of 3 chasers and 1 keeper on at all times. Their responsibility is to score goals through the 3 hoops defended by the other team. The positions are shown by the color of their headband, green for keeper and white for chasers.
When they score they earn 10 points, and it doesn't matter which side of the hoop they score from. The keeper and the chasers also play a key role in defending their own hoops from the other team.
Around the hoops the keeper get's immunity from the beaters when in defense, as well as being allowed to reach his or her hand through the hoop to stop a goal. This does not count for chasers.
Together with the chasers and the keeper you also have 2 beaters on pitch. They are recognized by their black headbands. The beaters use bludgers to help bolster their team's offense and defense.
The bludgers knock people out of the game temporarily. If a player is hit with a live bludger, they must let go of any ball they possess, dismount their broom, and tag one of their own hoops before re-entering play.
There are only three bludgers and four beaters, so it often takes strategic coordination for a team to have control of both bludgers.
Beaters are the only ones allowed to catch a bludger without getting temporarily knocked out of play.
SNITCH AND SEEKER
After 17 minutes, the snitch runner is released. The snitch runner is a neutral person dressed in yellow colors, and the snitch itself is a small ball secured to the back of the snitch runners shorts.
After 18 minutes the seeker is released in order to catch or defend the snitch. A catch gives the team 30 points and ends the game. If the 30 points makes the scores even, the game proceeds to overtime.
The seekers are not allowed to engage the snitch runner physically other than trying to catch the snitch, but the snitch runner is allowed to use all means necessary without risk of injury to keep the seekers away.