Foul Ball
A batted ball outside the lines, worth a strike unless you already have two.
What it actually is. A foul ball is a batted ball that settles outside the first or third base lines, or that goes past first or third base outside them, or that a fielder touches in foul ground. It counts as a strike unless the hitter already has two, in which case nothing happens and he bats on. A foul caught in the air is an out anywhere, including in the stands' front row if a fielder can reach it.
What somebody who knows the game gets out of it. The two strike foul is one of the few places baseball gives something for free, and good hitters treat it as an asset. Fouling off pitches he cannot drive is how a hitter survives long enough to get one he can, and it raises the pitcher's pitch count at the same time, which is a second currency entirely. The willingness to shorten a swing and stay alive with two strikes is a real and separable skill, and the hitters who have it post batting averages that their raw contact quality does not explain.
The numbers worth knowing. Roughly a sixth of all pitches thrown are fouled off. A ten pitch at bat that ends in an out has still cost a starter a meaningful part of the roughly one hundred pitches he is going to be allowed.
What people get wrong about it. The lines themselves are fair. A ball that lands on the chalk is fair, and the foul poles are fair too, which is why a home run off the pole counts. The name is one of the worst in sport. Also, a bunt fouled off with two strikes is a strikeout, which is the one exception to the free foul and the reason nobody bunts for a hit at 0-2.
At Little League and travel ball. At youth level the two strike foul is where at bats go to die, because the defense is usually one dropped third strike away from chaos anyway. Many youth fields also have very short foul territory, which helps hitters: a pop up that would be an easy out in a professional park lands in the parking lot and the at bat continues.
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