Channel manager: the details
Without one, every booking means closing that room by hand on all the other portals, and the delay ends in overbooking. With one, when a booking comes in through any channel it is deducted from inventory and the change reaches the rest within seconds. The same goes for rates and minimum-stay restrictions: they are defined once.
It works connected to the PMS, which knows which rooms exist and what state they are in, and to the website’s booking engine. Having every channel under control also lets you decide how much inventory to give each intermediary and how much to keep for direct sales, which pay no commission.