Modern baseball was put together in the United States in the 1840s, from older bat-and-ball games. By the late 1800s, big leagues had formed and people across the country went to the games. American children grew up playing it on every patch of grass they could find.
The pitch is a giant diamond shape. The pitcher stands in the middle and throws the ball as fast as they can to the batter standing at 'home plate'. If the batter hits the ball, they run as fast as possible to first base. If they keep going - all the way around first, second, third and back to home plate - they have scored a run. If they hit the ball so far that it goes out of the field, that's a 'home run', and they jog all the way around.
Baseballs are surprisingly small - about the size of a tennis ball - and the bats are long pieces of polished wood, usually made from ash or maple. Players wear leather gloves on one hand to help catch the ball. The catcher (who stands behind home plate) wears extra padding because the ball comes at them so fast.
Baseball is not just American any more. It is huge in Japan, South Korea, Taiwan, Cuba, the Dominican Republic and Venezuela. The Baseball World Cup brings teams from around the world together. Some of the best players in the US Major League come from Latin America, Asia and the Caribbean.