In baseball, a triple is a kind of hit whereby the batter reaches third base on a batted ball in play. Of the four broad types of baseball hits (single, double, triple, and home run), the triple is by far the rarest, due to the degree of difficulty in reaching third base before the fielders can retrieve the ball. This rarity, combined with the degree of difficulty and the high chance of being thrown out, make the triple one of the single most exciting plays in baseball. Personally, I would rank it as the fourth most exciting play in baseball, behind only the straight steal of home, the suicide squeeze, and the inside-the-park home run.
Triples have become increasingly rare over the course of baseball history. This is because ballparks (and especially, outfields) have shrunk over time, in order to bring fans closer to the action and also to generate more home runs. Now there is less space for the ball to bounce around, and the outfielders get to balls more quickly. Accordingly, most of the all-time triples records were set in the early part of the 20th century, when outfields ranged from massive to positively cavernous, and these records will likely never be broken.
Major League Triples Records
Most triples, single season:
NL: Chief Wilson (1912), 36
AL: Sam Crawford (1914), Shoeless Joe Jackson (1912), 26
Most triples, career:
ML: Sam Crawford, 309
NL: Honus Wagner, 252
AL: Ty Cobb, 295
Most triples, single game:
NL: 4, Bill Joyce, New York Giants, May 18, 1897
AL: 3, tie, 21 players