Run Batted in
A run that scores because of the batter's plate appearance.
What it actually is. Runs that scored on a hitter's plate appearance, whether by hit, walk with the bases loaded, sacrifice or ground out.
What a scout reads off it. It is the most context-dependent number in the box score. A hitter cannot drive in runners who were never on base, so a hundred RBI says at least as much about the two or three hitters ahead of him in the order as about him.
Where the lines are. A hundred RBI is the traditional marker of a middle-of-the-order bat. Hack Wilson's 191 in 1930 is the record and was set in the highest-scoring season of the twentieth century.
How it lies to you. The old argument that some hitters are clutch and rack up RBI beyond their opportunities has been tested repeatedly and has never held up over a career. Opportunity explains almost all of it.
Batter's Eye: look up anything in baseball