You may have heard that Abner Doubleday invented baseball in Cooperstown in 1839. In fact, that story is a myth. Doubleday was at the military academy at West Point that year, not in Cooperstown. A formal set of baseball rules came later. In September 1845, the New York Knickerbocker club published them.

Even with written rules, some plays confuse new fans. A force play happens when a runner must run to the next base because the batter has become a runner. On a dropped third strike, a batter can try to run to first base if first base is open or there are two outs. A double play is a play in which two runners or batters are put out.

Two more rules have strange names. The infield fly rule applies to a fair fly ball that an infielder can catch with ordinary effort when first and second base, or all three bases, are occupied before the second out. A balk is an illegal motion by the pitcher with runners on base, and every runner moves up one base.

Baseball keeps careful numbers. Babe Ruth hit 714 home runs in his major league career, and Hank Aaron finished his career with 755. Rickey Henderson stole 1,406 bases, the most in major league history as of November 2026. Nolan Ryan struck out 5,714 batters, also the most in major league history as of November 2026. Cy Young won 511 games, almost 100 more than any other pitcher in history, as of November 2026. Earned run average (ERA) is the number of earned runs a pitcher allows per nine innings.

The catcher crouches behind home plate and catches the pitches, and the pitcher stands on the pitcher's mound, in the middle of the infield. A pitcher and a catcher throw a lot, so a player should not do both jobs for the same team.

Young pitchers are protected by rules. Little League played its first official game on June 6, 1939. As of November 2026, it limits a 9- or 10-year-old pitcher to 75 pitches a day and an 11- or 12-year-old to 85. The more pitches a young pitcher throws in a day, the more days of rest he or she needs, as of November 2026.

Young pitchers should learn the fastball first and add a changeup once skilled. MLB's Pitch Smart advises players aged 9 to 12 to throw only fastballs and changeups. Shoulder or elbow pain in a young thrower should always be taken seriously. A player should never throw through it.

Words to know

• myth: a false story
• force: a must-run play
• balk: illegal motion
• changeup: slower pitch
• infielder: a fielder