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.
There are nine innings in professional baseball games (sometimes fewer in lower levels), and each inning is divided in half.
In the top of an inning, the visiting team hits and the home team plays defense.
In the bottom of the inning, the home team hits and the visiting team plays defense.
There's no doubt that baseball and softball are complex games that are tough for a person to learn if they haven't followed it for their entire lives.
There are many, many more rules than the ones below, and exceptions to just about every one of them.