I am interested in both, but it is similar to Hockey in the minor leagues, though baseball has a lot more of them. Each team has at least 1 rookie league team, usually 2 A ball teams, 1 AA team, 1 AAA team, then the major league team
How they work all that with the roster rules is really interesting to me .. especially for a team like the Cubs that pretty much blew up the entire team after a good (but not good enough to win it all) run and rebuilt with young players. The Yankees look like they are about to do that, but probably not blow up it up as much.