Number of singles.

Number of doubles.

Number of triples.

Number of at bats.

The percentage of pitches thrown / seen in a count favorable to the player. Defined for pitchers as 0-1, 0-2, 1-2 and 2-2 counts. For hitters it is 1-0, 2-0, 3-0 and 3-1 counts.

Batting average.

Stands for batting value. It is determined by taking the player's park-adjusted wOBA and subtracting away the league average wOBA, and then dividing that by 1.15 and multiplying by the number of plate appearances the batter has had.

The number of unintentional walks.

Number of batters faced.

The reverse of Ahd.

The number of batted balls.

The percentage of pitches swung at, that are contacted.

The percentage of pitches swung at, where contact is made.

The percentage of pitches thrown / seen in a count deemed even. Defined as 0-0, 1-1, 2-1 and 3-2 counts.

The percentage of batted balls classified as a fly ball.

Stands for Fielding Independent Pitching, a more simplistic version of xRA's goals. It is (13*HR + 3*(BB+HBP) - 2*(SO)) / IP + a constant, usually around 3.2.

The percentage of batted balls classified as a ground ball.

Number of times grounded into a double play.

The number of hits.

The number of hit batters.

The number of home runs allowed or hit.

The percentage of fly balls and line drives that go for a home run.

The percentage of batted balls classified as an infield fly.

The number of innings pitched.

The percentage of batters faced / plate appearances that resulted in a strikeout.

The percentage of plate appearances ending in a called strikeout.

The percentage of strikeouts resulting from a swing and a miss (pitcher) or the percentage of plate appearances ending in a swinging strikeout (batter).

The percentage of batted balls classified as a line drive.

The average leverage index for all plate appearances by the pitcher / hitter.

The percentage of batters faced / plate appearances that resulted in either an unintentional walk or hit batter.

On Base Percentage.

The percetange of pitches swung at outside the strike zone, that were made contact with.

OBP + SLG.

The percentage of pitches thrown outside the strike zone, that were swung at.

The percentage of pitches thrown outside the strike zone, taken for a called strike.

Number of plate appearances.

Stands for plate appearance value. It is used to give credit to the hitter for the difference between average and replacement level for those that wish to use a WAR-style calculation. The difference is set to 20 runs per 600 PAs.

The percentage of fly balls hit to the batter's pull side.

The number of pitches thrown.

Stands for position value. It gives credit for the position that the player plays, but not his quality of play there. That is, this is not about how well a player plays defense, merely where a player plays defense. The values per full season (defined as 5,850 defensive PAs [150 games x 39 PAs per game]) are: +12.5 for catcher, +7.5 for shortstop, +2.5 for second base, third base and center field, -7.5 for left and right field, -12.5 for first base and -17.5 for designated hitter.

Total pitches seen divided by plate appearances.

Runs above average.

The percentage of balls in play (i.e. not including home runs), that result in the batter reaching base, either via hit or error.

Number of times reaching base via error.

Stands for run value per 600 PAs. It is batV divided by PA multiplied by 600. 600 PAs is considered the bench mark for a full season.

Number of sacrifice bunts.

Slugging Percentage.

The number of strike outs.

The percentage of pitches thrown that result in a strike or batted ball.

The percentage of pitches seen, swung at.

The percentage of pitches, swung at and missed.

wOBA or weighted on base average is a statistic developed by and used with the permission of Tom Tango. He gives a detailed rundown of it here. In a nutshell, wOBA uses linear weights on certain batting events to come up with a metric that is scaled onto an OBP scale.

wOBA* divided by the league's average wOBA.

This is wOBA, but corrected for the parks the batter has played in that season.

The expected number of home runs allowed or hit based on the park factors and the distribution of batted balls.

The expected number of innings pitched, it is expected outs from the xRA calulations divided by 3 .

The expectd number of runs allowed, from the xRA calculations.

Stands for expected Run Average. xRA assigns run and out values to events under a pitcher's control and then constructs a run average using expected runs divided by expected outs multipled by 27, the same scale as the more common ERA or RA. See here for more detail

Like wOBA+. xRA+ is equal to the player's xRA subtracted from league's xRA and then divided by the league's xRA. That is then added to one and then multiplied by 100. As a formula it is: ( ( ( league xRA - player xRA ) / league xRA ) + 1 ) * 100.

The percentage of pitches swung at in the strike zone, that were made contact with.

The percentage of pitches with locations recorded landing within the typically called strike zone as defined by pitch F/X. The dimensions of the typically called strike zone vary.

The percentage of pitches thrown in the strike zone, and taken for a called ball.

The percentage of pitches thrown in the strike zone, that were swung at.