How does Hotel.com, Booking.com etc. Work?

[deliengs]

Hi Guys
I hope i'm posting this in the right section.

I was wondering,
How does Hotels.com, Booking.com, Expedia.com, agoda.com and the rest of them work in terms of having so many hotels on them.
Do these websites/companies buy hotel rooms in bulk? Or How do they get prices from all the hotels around the world?

I'm thinking the bulk option is a little more difficult because you can't buy like a room in nearly every single hotel around the world.

Any ideas?

Thanks!!

 

[MKFrost]

The just act as an agent for the hotels

 

[tridev]

The hotels probably have APIs that you can register as a 3rd party booking agent so you get their availability and do bookings on your site on the fly.