Each batter has four different stats.

"Hitting" corresponds to his ability to hit the ball with a straight shot.
"Power" represents the batter's strength. The higher the power, the farther the ball can be hit.
"Speed" shows how fast the batter can run the bases.
"Bunt" displays his bunting strength.

Pitchers have three stats.

"Arm" determines how hard he throws the ball.
"Control" determines the pitcher's accuracy.
"Stuff" represents the his ability to throw tricky pitches.