Fair territory

In baseball, a fair ball is a batted ball that entitles the batter to attempt to reach first base. In order for a batted ball to be fair, it must be hit in such a way that it:

Fair territory or fair ground is defined as the area of the playing field between the two foul lines, and includes the foul lines themselves and the foul poles.

On a fair ball, the batter attempts to reach first base or any subsequent base, runners attempt to advance and fielders try to record outs. A fair ball is considered a live ball until the ball becomes dead by leaving the field or any other method.

By contrast, a foul ball is a batted ball that does not entitle the batter to attempt to reach first base.

...
Wikipedia