The squad in the field is the defensive team; they attempt to prevent the baserunners from scoring. There are nine defensive positions, however, only two of the positions have a mandatory location (pitcher and catcher), the locations of the other seven fielders is not specified by the rules, except that at the [...]

A simplified version of the rules of baseball is at simplified baseball rules. The complete Official Rules can be found www.mlb.com, the official web site of Major League Baseball in the United States.
General structure
Baseball is played between two teams of nine players each on a baseball field, under the authority of [...]

Origins of baseball
The distinct evolution of baseball from among the various bat-and-ball games is difficult to pin down. However, it is mainly agreed that modern baseball is an American development from earlier British games, such as rounders, with possible influences from cricket.
The earliest known mention of the sport is in a 1744 [...]