P: Pitcher (Position "number" 1). While the primary role of a pitcher is to pitch the ball, he must also be able to field his position. This consists of fielding ground balls and bunts up the middle of the diamond, and running to cover first base on any batted ball that pulls the first baseman out of position.
C: Catcher (2). He must catch, or at least block, all the pitches to prevent baserunners from advancing, in addition to preventing stolen bases with a strong throwing arm. He must also catch pop-ups into the foul territory behind the baseline, and tag out runners who are attempting to score, while blocking their access to home plate.
1B: First Base (3). The first baseman's job, in addition to fielding balls hit in his direction, is primarily to catch throws from the other infielders (2B, 3B and SS) in order to retire the batter and prevent him from getting on base. When a runner is on first base, the first baseman will tend to stand on or near the bag, holding the runner close to prevent the runner from stealing second base.
2B: Second Base (4). Second basemen have an important defensive role to field ground balls hit toward him and, if necessary start a double play. When the ball is hit to the shortstop, the second baseman will help "turn" a double play by stepping on second base, fielding the throw from SS, and throwing to first base, to retire both the batter, and the runner on first.
3B: Third Base (5). Third base is known as "The Hot Corner", since most right-handed hitters will tend to hit the ball hard in this direction. The third baseman must be able to field ground balls and throw strongly to first base, as well as cover fly balls in fair and foul territory.
SS: Short Stop (6). Shortstops, like the second baseman, must field ground balls and start or turn double plays. In addition, they need a stronger arm as the throw to first base is further from the shortstop side.
LF: Left Field (7), R & L CF: Right & Left Center Field (8), RF: Right Field (9). The role of the outfielders is to chase down and catch any ball hit into the outfield and, if necessary, make a rapid and accurate return throw, either to a base or to the "cut-off man", a infielder who has moved into a position specifically to make a relay throw.