These firms effectively operate as a collective for the benefit of the partner class. New partners must invest capital, ongoing partners get returns, and older partners retire with a terminal payout. Some partners may take on expanded leadership roles and get higher annual payouts.
The overarching legal structure is a sort of "modularization" to limit the liability of lawsuits and enable flexible operation. There is a usually a global partnership council that dictates universal operating norms and practices.
Again, fundamentally, it operates as a collective and international units support each other for collective benefit.