Oh, yeah, baseball's a sport that developed in my world--my home country, even--about six, seven hundred years ago, from my time. Two teams trade off offense and defense throughout a nine-inning game. On offense, you get a bat, and your job's to hit the ball that the pitcher throws and run the bases in order so you can score points. On defense, you catch the ball and throw it to other players on your team in order to get the batter out by tagging 'em or getting to a base before they can reach it.

...It'd be easier to explain if a game were going on. It gets kinda complicated. Lot of strategy involved.