There are all kinds of waivers for all different occasions. But essentially, here is how waiver deals can be made between Aug. 1 and the Aug. 31 deadline for setting potential playoff rosters:
Virtually every player in the major leagues will be placed on waivers this month, whether a team intends to trade that player or not. If nothing else, the sheer volume of names can at least disguise players whom clubs do want to sneak through so they can be dealt.
If a player isn't claimed by any team in either league, he can be traded until the end of the month to anyone.
If a player is claimed, but only by one team, the player can be traded only to the team that claims him.
If a player is claimed by more than one team, the club with the worst record in that player's league gets priority -- and the player can be traded only to that team.
If a player is claimed only by teams in the other league, the club with the worst record in the other league gets priority -- and the player can be traded just to that team.
If a deal can't be worked out or the team doesn't want to trade that player, he can be pulled back off waivers once in August. If he is placed on waivers again before September, he can't be recalled a second time.
Or, if a team is just hoping to dump a player's salary, it can simply allow a team which claimed that player to have him for a small waiver fee. If that happens, the team that gets the player has to pay his entire salary. That's how the Yankees were stuck with Jose Canseco and the Padres were stuck with Randy Myers in recent years: They claimed those players, thinking they were just blocking other teams from getting them. Instead, their old clubs said: "You claimed him. You got him."
In the past, many teams claimed players just to keep them from being traded to contenders with a better record. This year, that isn't expected to happen as often, because most teams can't afford to get stuck with a big contract if they're awarded a player they really didn't want.