Here are some simple definitions for the statistics you can find in weekly updates and player profiles.
G – Games (試合): When a player makes an appearance (a) on the field as a defender, or (b) at the plate as a hitter or (c) on the bases as a pinch runner, he is counted as having played in the game.
AB – At Bats (打数): Not every plate appearance counts as an at bat! If a player (a) earns a walk, (b) gets hit by a pitch, (c) advances a runner with a bunt, or (d) brings a runner home on a fly ball, it does not count as an at bat.
R – Runs (得点): Any time the runner crosses home plate safely, whether he hit the ball or got on base in some other way, or even if he replaced another runner, the run is credited to him.
H – Hits (安打): When a player reaches base safely after making contact with the ball, he is credited with a hit. Regardless of the base he stops at, the hit counts the same in this particular category.
2B – Doubles (二塁打): When a player’s hit results in his advancing all the way to second base, it is called a double. Exceptions are made when a fielder’s error allows him to reach second, or when he advances when a fielder is trying to throw out a runner at a different base.
3B – Triples (三塁打): When a player’s hit results in his advancing all the way to third base, it is called a triple. Exceptions are made when a fielder’s error allows him to reach third, or when he advances when a fielder is trying to throw out a runner at a different base.
HR – Home Runs (本塁打): When a player reaches home plate on his own hit, without benefiting from a fielding error, it is called a home run. Typically, home run balls are hit over the outfield fence, although on occasion a player manages to run around all the bases before the outfielders can throw the ball back to home plate. (This is called an inside-the-park home run, not a “running home run” as it is called in the Japanese game.)
RBI – Runs Batted In (打点): When a base hit, walk, sacrifice fly, or ground out results in a runner crossing home plate and scoring a run, the batter gets credit for a run batted in. Exceptions are when the hit ball results in a double play or an error.
BB – Walk (四球・敬遠): When the pitcher throws four pitches outside the strike zone (balls) that are not swung at, the batter is allowed to take first base uncontested. This is called a walk. Sometimes, a pitcher will intentionally walk a batter, either because he poses a threat to do worse than reach first base, or because it allows the team to try to get a double play (two outs on one play) from the next hitter.
K – Strikeout (三振): When a batter misses three good pitches (either by swinging at a pitch, not swinging at one in the strike zone, or hitting a foul ball), he strikes out. The third strike, though, cannot be a foul ball, unless it is a failed bunt attempt. If the batter has two strikes and hits a foul ball, he remains at two strikes until he swings and misses, lets a good pitch go past him, or the at bat ends with another outcome.
SB – Stolen Base (盗塁): When the batter reaches base safely, and then successfully takes another base by running to it while the pitcher is delivering a throw to the mound, he is credited with a stolen base.
CS – Caught Stealing (盗塁刺): When the runner’s stolen base attempt fails, either by being thrown out by the catcher or another fielder, he has been caught stealing.
AVG – Batting average (打率): A batter’s total number of hits divided by his number of at bats (not plate appearances!) gives us his average. Walks do not count for or against a hitter’s average, nor do sacrifice bunts or flies.
OBP – On Base Percentage (出塁率): A batter’s total number of times on base (excluding by error) divided by his total number of plate appearances.
SLG – Slugging Percentage (長打率): This statistic takes the number of bases a player advances on his own hits, and divides it by the number of at bats. Hence, if a player hits a single in his lone at bat, his average and slugging percentage will both be 1.000. However, if he hits a home run in his next plate appearance, he will have reached 5 bases in two at bats, giving him a slugging percentage of 2.500.
OPS – On Base Plus Slugging: Simply add the OBP and SLG to get this figure.