This is a baseball term which refers to the positions that make up the interior defense of a team. These players are in positions around the diamond and include the 1st, 2nd, and 3rd basemen, pitcher, catcher, and shortstop. Excluded from the infield are outfielders (right, center, and left). An infielder is part of the primary defense of the team, and is tasked with being the first line of defense if a ball is hit. There are many different skills needed to be an effective infielder, such as hand-eye coordination, a good throwing arm, great catching ability, speed, and agility. There are a few different spots on the baseball diamond where each position is likely to be, depending on the defensive strategy employed at the time.
The individuals tasked with manning the bases are not always standing right next to them. If there is a runner on base, the defensive player will typically stand closer to the base. However, if there are no runners on base, the infielders are usually positioned in a way that prevents a hit ball from going through one of the gaps that exist between the defense. The first baseman stands back and to the left of the base, while the second baseman typically stands to the right of the base, and stands back about as deep as the first baseman. The shortstop is positioned on the other side of second base, and usually plays in the middle of dirt on the infield. The third baseman will play to the right of the base, usually in line with the shortstop. The pitcher is always positioned on the pitcher's mound, and the catcher is always behind home plate. There is an award for defensive players, called the Golden Glove, and it is not limited to infielders and excludes pitchers.