From Wiki Gonzalez
Baseball's amateur draft is an annual summer event for adding amateur talent to organized baseball. It was instituted in 1965 as a way to control MLB teams from staging expensive multi-team bidding wars over unproven, unsigned players, and has been regarded as a prime force behind competitive balance.
The draft consists of multiple rounds. Each team gets one pick per round. Draft order is determined by order in the previous year's standings, worst to best. Trading draft picks is not allowed, but teams can pass on a pick. The draft ends when every team in the round has passed.
When a player is drafted, he is restricted to negotiating a contract with the team who drafted him. If the team and player cannot reach an agreement by a specific date, the player is released from his restrictions and can re-enter next year's draft.
A team can receive picks of another team as compensation when the other team signs away their free agent who belongs to one of the various free agent classes. Besides getting those other picks, they may receive extra "sandwich picks" between draft rounds.
Currently amateurs (high school players and collegians) from the United States, Canada, and Puerto Rico are draft-eligible. Note that Asia and the rest of Latin America (including Cuba) are not included, hence bidding wars for prime baseball talent persist, and amateur talent from those regions usually signs with the highest bidder.
MLB, unlike the NFL and NBA, has not chosen to make their draft a televised spectacle -- it is conducted on a weekday via conference call. This state of affairs has necessitated BTF draft threads which track progress in almost realtime. In general Primates have found the long threads informative and exciting, contributing to BTF's effect on the American economy.