On Offense

Each team has nine players in its batting order, and they must stick to that order throughout the game (players may substitute in for other players). A play begins with a batter waiting to hit a pitch from the pitcher. If the batter hits the ball into the field of play, the batter runs to first base and can run to as many bases as he or she deems fit without getting out.
A batter gets three strikes (a swing and a miss or a ball over the plate in whats deemed the strike zone by an umpire) or he or she is out. If there are four balls (a pitch that is not in the strike zone), the batter is automatically allowed to go to first base.
When a batter begins running, he or she is then referred to as a runner. Runners attempt to reach a base, where they are safe and can remain on the base until the next hitter comes up. The defensive players attempt to prevent this by putting the runners out using the ball; runners put out must leave the field.
A batter gets a hit when he or she reaches a base without getting out, or forcing another runner to get out (and without the defense making an error). Runs are scored when a player completes a circuit of the diamond before there are three outs in the inning.
If a players hits the ball over the outfield fence in fair territory (between the foul lines), its a home run, and the batter can circle all four bases.