New to this topic... What does being a partner carrier mean?

First off, I apologize if I'm posting this in an incorrect forum--as you will see, I'm not the most knowledgeable on "all things trucking." I would appreciate if anybody would be able to provide me clarity onto what a partner carrier relationship entails? From what I've read so far, an O/O--also a power only driver if I'm not mistaken--essentially works with or for a larger carrier to transport a shipment using another carrier/shippers trailer. With this partner carrier relationship, are O/Os literally leasing their vehicles and services to the larger carrier? Or are O/Os receiving a percentage of the haul? Or maybe both? Do these vary from relationship to relationship? Are O/Os allowed to do independent work and/or work with other carriers while being signed on with a certain carrier?

Basically to sum it all up, what does a typical partner carrier relationship look like--insurance/financially, liability, etc.

Any help is appreciated! Thank you!