Introduction to Indoor Hockey
Indoor Hockey is a version of Outdoor or Field Hockey. It was developed in Europe in the 1950s mainly to allow keen hockey players to continue enjoying their sport during periods of bad winter weather. But as it is an exciting and enjoyable version of the game it is now played in many locations around the world. It can actually be played on any hard, smooth and flat surface but is usually played in a sports hall.
The pitch is therefore smaller than an outdoor field. It is only 44 meters by 22 meters at most. Something else which distinguishes an indoor pitch from an outdoor one is that indoors there are 10cm boards down the longer pitch side-lines. This keeps the ball in play more and so helps to create a fast, flowing and exciting game.
For indoor hockey, two teams of 6 players compete against each other using their 'hooked' sticks to play a small, hard, often white but sometimes colored, ball. In indoor hockey the ball may only be pushd and not hit or flicked. Except for a shot at goal, it may only be played along the ground. Players skillfully push, pass and dribble the ball.  But, as in field/outdoor hockey, the fundamental aim of the game is score by getting the ball into the opponents' goal. To do that, they have to get the ball past the other team's goalkeeper, who protects the goal, and logically, tries to keep the ball out!
An Indoor Field Hockey Pitch. Image by Laurent van Roy, distributed under a CC-BY 2.0 license.
Player Positions
As already mentioned, every team must have a goalkeeper. The other 5 players are referred to as 'field players', and are dispersed over the pitch. The field players can be put into two general categories - attackers and defenders. While no player (other than the goalkeeper) has an exclusively defined role, the attackers are generally on attack, the defenders are generally on defense - but in indoor hockey you also get exciting overlaps from defense into attack
Stick Handling
An essential skill necessary for playing hockey is the ability to control, pass, push, stop and shoot the ball with your hockey stick. This is known as stick work, or stick handling. It is both beautiful and impressive to watch a player with good stick handling skills control the ball while dribbling the length of the pitch and especially to weave through the sticks and legs of defenders to create an open shot.
It is important to know that the head of a hockey stick has a rounded side (the right-hand side) and a flat side (the left-hand side). It is only with the flat, left-hand side of the stick and the edges of that side that you are permitted to play the ball.
No Feet!
It may seem like common sense, but it is worth mentioning that in indoor hockey just as in outdoor hockey, field players are not allowed to use their feet (or any other parts of their bodies for that matter) to control the ball. Only the goalkeeper is allowed to use hands, feet, etc. to stop or propel the ball when defending in his or her own circle.
Scoring a goal in hockey is very interesting. There are only certain ways it can be done: from a Field Goal, from a Penalty Corner, and from a Penalty Stroke.
Field Goals
A field goal is a goal scored from open, continuous play. Field goals may only be taken from the 'shooting circle', a roughly semi-circular area in front of the opponents' goal. If a ball is played from outside the 'shooting circle' and it goes directly into the goal or is only touched by a defender on the way, it does not count as a score.
Penalty Corners
If a defending team breaks certain rules, the other team may be awarded a 'penalty corner.' It is awarded when a team breaks a rule while defending in their 'shooting circle'. It can also be awarded when a defender is guilty of a particularly bad foul in the defending half of the pitch.
To take a penalty corner, play is stopped to allow the teams to take their positions in attack and defense. One attacker stands with the ball on a designated spot on the back-line. (It's the line that marks the shorter boundary of the pitch and on which the goal is placed.) This player will 'push out' the ball to other attackers, waiting to take a shot at goal. The other attackers usually wait at the top of the shooting circle to receive the ball. But in any case, all attackers have to be outside the shooting circle until the penalty corner begins.
All members of the defending team (including the goalkeeper) position themselves behind the back-line to defend against the penalty corner. Only the goalkeeper is allowed to position her/himself inside the goal. All other defenders must be outside the goal on the side furthest from where the ball is being put into play.
The ball is 'pushed out' to an attacker waiting to receive it. Before a shot on goal can be taken, the ball must first travel outside the circle. The receiver then usually pushes it back into the circle for the a shot either by her/himself or another attacker.
Once the attacker on the back-line begins to push the ball out, the defenders on the back line may move into the circle, and do their best to stop the other team from scoring.  But quite a lot of the time a goal is scored and one team of players will be celebrating!  It's a long explanation, but in practice, it all happens very quickly, and is exciting to watch.
Penalty Strokes
A penalty stroke is a shot taken on goal by a chosen player and defended only by the goalkeeper. (All other players must stand in the other half of the pitch.) A penalty stroke may be awarded for a few reasons, the most common being an offence by a defender in the circle to prevent the probable scoring of a goal. The shot is taken from a spot 7 metres directly in front of the goal. Match time is stopped when a penalty stroke is being taken.
Duration of a Match
A regulation length indoor hockey match lasts 40 minutes - which is broken into two halves of 20 minutes each. The team with the most goals at the end of the 40 minutes is the winner. It is also possible for a match to end in a draw (or tie). But in some matches - like in a tournament or in a championship game - there must be a winner. In those cases, a match which is tied at the end of regulation time, then often goes into over time (the first team to score in over time wins), and if necessary, to a penalty stroke competition.