Channel Manager integration

Hey…
I am looking for a help on how to integrate live inventory from a channel manager like reseliva.com, Lodgeit & eZee Centrix, I am not sure how booking.com agoda.com is getting inventory from channel manager. But I would like to use a channel manager on my own site.

Can anyone help me to teach how that thing is working? I need to know how it works technically and how the integration is done.

Thank you in advance?