my understanding is where PM is working..

Performing Organization is the company providing services or building product for the client. In buyer . seller relationship generally it is referred to seller. Buyer is procuring the services.

The project manager as per PMI, is from buyer organzation unless it is mentioned otherwise in the question. Like we have to assume organziation as Matrix orgnization unless specifically mentioned project org or strong matrix org etc.

So you have read the PMBOK / or any other reference books at least once so you get your doubt clarified on your own.

Regards

CN Patil