I have been reading a lot in other threads concerning award tickets on other airlines, YQ fees, etc.

I have a question for my own educational purposes:

How exactly does Delta "settle up" with partner airlines when Delta customers redeem their Delta miles for award tickets on partner airlines?

Example: I just redeemed a JFK-HKG trip in Business class on Korean Air at 120,000 DL miles and $91 in tax.

How does Delta reconcile that with KE? Do they pay money to them or does it cancel out when a KE customer uses their miles on Delta, etc.? Does DL even reveal how this works?

I am trying to understand the process and what it might actually cost Delta in real money for my BE trip on KE for 120,000 miles and $91 in "tax/fees"

Thanks!