Positions
Seeker:
probably the most important one on the team, and it is to catch the Golden Snitch before the opposing team's Seeker, thus ending the game and winning 150 points for his or her team. This almost always means that the successful Seeker's team wins.
Keeper:
Protect the team's goal hoops by flying in front of them and stopping the opponents from throwing the Quaffle through them.
Beaters:
protect the rest of the team from the Bludgers by hitting them at the other team with a wooden bat (like a baseball bat), which they hold in one hand. They are usually the biggest and strongest of the team. They are not allowed to hit the Bludgers at the crowd, the referee or the Keeper (unless the Quaffle is inside the scoring area).
Chasers:
Keep possession of the Quaffle, and try to score a goal (worth ten points) by throwing it through one of the opponents' three hoops. They can pass it among themselves, but only one player is allowed in the scoring area at any one time
Balls
Quaffle:
Spherical in shape, scarlet in color, and approximately 12 inches (30 cm) in diameter, and about the weight of a football but hollow. It is enchanted to fall very slowly through the air when dropped to prevent players from having to continuously dive to retrieve it. The Quaffle is also enchanted to make it easy to grip with only one hand. There is only one quaffle and if the chaser throws it through the hoop they score 10 points for their team.
Buldgers:
There are two Buldgers in the game of Quidditch. They are round, jet black balls, made of iron and 10 inches (25 cm) in diameter. Bewitched to fly without any visible means of propulsion, they retain inertia, which makes them unable to change speed or direction swiftly. They act as airborne obstacles, flying around the pitch and trying indiscriminately to knock players off their brooms. Bludgers do most of the damage in the game of Quidditch; they will occasionally injure players and break brooms. A correctly bewitched Bludger with no jinxes will not side with a team; they will instead alternate players after they try and knock a player from one team off their broom.
Golden Snitch:
Often referred to as simply the Snitch, it is a small golden ball the approximate size of a walnut (roughly 1 inch (2.5 cm) in diameter) with silver wings. The winged Snitch is enchanted to hover, dart, and fly around the pitch, avoiding capture while remaining within the boundaries of the playing area. Having "flesh memory" the Snitch is able to recall the first person who touched it, and will respond only to the first person who caught it. This helps when there is a dispute about who caught the Snitch first.
Gameplay
The game starts with the referee releasing all four balls from the central circle. The Bludgers and the Snitch, having been bewitched, fly off on their own accord; the Snitch to hide itself quickly, and the Bludgers to attack the nearest players. The Quaffle is thrown into the air by the referee to signal the start of play.
Chasers score by sending the red, football-sized Quaffle through any of the three goal hoops. Each goal scored is worth ten points. After a goal is scored, the Keeper of the team scored upon throws the Quaffle back into play. Capturing the Snitch earns the Seeker's team 150 points, equivalent to 15 goals scored by Chasers. Since the game ends immediately after the Snitch is caught, the team capturing the Snitch is very likely to win the game. However, teams are ranked according to points scored, not games won. . Since teams are ranked according to points scored, a team that knows it cannot hope to catch up to the winning team might favor quickly catching the Snitch so as to end the game before any more points are scored and hence reduce the lead in point difference obtained by the winning team, so that it is easier to win them back in subsequent matches.
All seven players must constantly avoid both being hit by the Bludgers (which attempt to attack them) and accidental contact with the Golden Snitch (which is a foul if anyone but a Seeker touches it).
As the game can be difficult to follow by the crowd, due to the high speed and maneuvering of the players, games will usually be commentated.
The length of a Quidditch game is variable, as play can only end with the capture of the Golden Snitch by one of the Seekers or by mutual consent of the two team captains. The game length is therefore determined largely by the Seekers' abilities. Games can go on for days, and even months, if the Snitch is not caught.
Rules
1. Bounderies
Players must not stray over the boundary lines of the pitch, although they may fly as high as desired. The Quaffle must be surrendered to the opposition if any player leaves the boundary (it is unknown what the penalty is if a player on defense leaves the pitch).
2. Time Outs
"Time out" may be called at any time by the Captain of a team. Time out may be extended to two hours if a game has already lasted for more than twelve hours. Failure to return to the pitch after this time will lead to the team being disqualified.
3. Penalties
Penalties can be awarded to teams by the referee. A single Chaser may take the penalty by flying from the central circle towards the scoring area. The opposing team's Keeper may attempt to stop the shot being scored, but all other players must not interfere (it is unknown if the Seeker may still attempt to catch the Snitch while a penalty is being attempted).
4. Contact
Contact is allowed, but a player may not seize hold of another player's broomstick or any part of their anatomy.
5. Substitutions
No substitution of players is allowed throughout the game, even if a player is too injured or tired to continue to play.
6. Wands
Players may take their wands onto the pitch, but they must not be used on or against any players, any players' broomsticks, the referee, any of the four balls, or the spectators.
7. Games End
A game of Quidditch will only end once the Golden Snitch has been caught, or at the mutual consent of both team Captains.
8. Quaffle Blocks
Only the Keeper can block Quaffle shots thrown by the opposing team.
Fouls
Blagging:
Seizing the opponent's broom tail to slow or hinder. (All players)
Blatching:
Flying with the intent to collide. (All players)
Blurting:
Locking broom handles with the intent to steer an opponent off course. (All players)
Bumphing:
Hitting Bludgers towards spectators. (Beaters only)
Cobbing:
Excessive use of elbows towards opponents. (All players)
Flacking:
Pushing any portion of anatomy through the goal hoop in an attempt to push the Quaffle out - the Keeper should defend from the front, not the rear. (Keepers only)
Haversacking:
Hand still on the Quaffle as it goes through the goal hoop - the Quaffle must be thrown through the goal. (Chasers only)
Quaffle-pocking:
Tampering with the Quaffle - e.g. puncturing it so that it falls more quickly or zig-zags. (Chasers only)
Snitchnip:
Any player other than Seeker touching or catching the Golden Snitch. (All players but Seeker)
Stooging:
More than one Chaser entering the scoring area. (Chasers only)
Winning
A game can only be won by a lead of 160 points or when the Golden Snitch is caught.
*Information from the Harry Potter and Quidditch Wikis
