The match takes place in two half's lasting approximately 10 rounds game time. (like soccer the referee's decide the official ending time each half.)
After every score and the start of each half, the team that scored (or lost the toss) kicks off to the opposing team. The recieveing team then proceeds to try and march down the pitch and either kick, shoot, or rush for points. Their attempt is deemed over when the opposing team takes the ball away, via intercepting it, stripping it, or recovering it. In the event of a scrum or possession by two teams, a jump ball is declared.
8 players are allowed on the pitch per team at any one time. Players may leave the pitch during the action and have a reserve sub in at any time, but the player is required to leave the field via the sub box before the other player can enter.
(think like hockey when they change lines)
If a player is knocked unconcious they remain on the pitch until either a jump ball, a score, or one of their team mates dragging them from the field of play occurs.
(indeed a solid strategy to score the big points is to indeed knock the opposing team unconcious for the easy tries.)
The red zone - the final 10 feet on the pitch on either side is the 'red' zone. Any player with the ball who is tackled to the ground in the red zone with the ball has the play blown dead, the opposing team immeadiately gains possession of the ball in a sort of free kick restarting play.