Players in the Olympics have generally played baseball since they were small children. Almost all of them are professional baseball players who progressed through youth leagues, high school and college baseball. (Some players skip college and are drafted into the pro ranks out of high school.)
Professional players in the United States were almost all drafted by a major-league team – the draft is held each June - and then play in the minor leagues. If they're good enough, and only a small percentage are, then they make one of the 30 major-league teams.
Because the U.S. Olympic team only will pick 25 players from throughout the country, many of the players in the Olympics, especially on the United States team, will play in the majors someday.
