AHL is NOW the minor league for the NHL. Originally it was another league, like the AFL/NFL were back in the day. Now each AHL team is tied to a NHL team for player "upgrades". A player can only play for 5 or 7 seasons for the AHL, and can be upgraded to NHL or downgraded back at any time. So if a player is acting like shit, he can be sent to the AHL, and if he doesnt improve he will end up getting traded for piss change or end up retiring.
Better now than before in many ways. Unfortunately the good teams lose players quickly and for good usually. Only a small number of Admirals got promoted and demoted.