First base, or 1B, is the first of four stations on a baseball diamond which must be touched in succession by a baserunner

Baserunning

In baseball, baserunning is the act of running around the bases performed by members of the team at bat.In general, baserunning is a tactical part of the game with the goal of eventually reaching home to score a run. In fact, the goal of batting is generally to produce baserunners, or help move...

 in order to score a run

Run (baseball)

In baseball, a run is scored when a player advances around first, second and third base and returns safely to home plate, touching the bases in that order, before three outs are recorded and all obligations to reach base safely on batted balls are met or assured...

 for that player's team. A first baseman is the player on the team playing defense

Baseball positions

There are 9 fielding positions in baseball. Each position conventionally has an associated number which is used to score putouts...

 who fields the area nearest first base, and is responsible for the majority of plays made at that base.

In the numbering system used to record defensive plays, the first baseman is assigned the number 3.

Also called first sacker or cornerman, the first baseman is ideally a tall player with good flexibility and quick reflexes.