The Primary Production Company (PPC) is responsible for organising an exhibition at the first (if touring) or only venue (if not touring).  It must also be responsible for the following at the first or only venue:
Creative and technical decisions
Contractual agreements
Producing and running the exhibition
Deinstallation and closing the exhibition
A Secondary Production Company (SPC) is responsible for organising an exhibition at the second or subsequent venues for a touring exhibition.  It must be responsible for the following at its venue:
Production and running the exhibition at that venue
Deinstalling the exhibition at the venue