Rules & Objectives
Baseball is a game between two teams of nine players each, under direction of a manager, played on an enclosed field in accordance with these rules, under jurisdiction of one or more umpires.
The objective of each team is to win by scoring more runs than the opponent.
The winner of the game shall be that team which shall have scored, in accordance with these rules, the greater number of runs at the conclusion of a regulation game.
One team players offense by having one person at a time batting. The second team or opponent plays defense with nine players on the field at one time to prevent the batter from getting on base and scoring runs.
There are nine innings in professional baseball games (sometimes fewer in lower levels), and each inning is divided in half to the top of the inning (when the visiting team hits and the home team plays defense) and the bottom of the inning (when the home team hits and the visiting team plays defense).
Each team gets three outs in each half of the innings.
The part of the field closest to the bases is called the infield, and the grassy farther reaches is called the outfield.
The bases are 90 feet apart on the diamond, closer in children's leagues and softball. Other fields are variable, and the outfield fences or the amount of “foul territory” - the amount of ground that borders the field between the long white lines that connect first base to home plate and third base to home plate – varies from field to field.
picture courtesy of Official-rules.org
image courtesy of baseballfielddesign.com
references: MLB.com, About.com