Platforms
Booking.com
The global giant, hotel-shaped, with the highest commission and the loosest guests.
Why you care
It brings international and last-minute demand you will not get anywhere else, at a price: commission is usually 15%, cancellation is easy, and payment handling is its own subject.
Worked example
A $1,400 booking nets roughly $1,190 after 15%. Worth it for nights that would otherwise sit empty; painful as a primary channel.
Taught in The OTAs