Think of the service catalog as a library of reusable components like LEGO(TM) blocks. Everything is designed to fit together. You may have something like a service catalog already in place or inside your organization. When you work with a service provider, services are delivered out of the service catalog. Whether it’s 10 services or 1,000 services, they come out of the service catalog.
Important Note: It’s important for the system architects to “own” the service catalog. The operations people can deliver consistently because the same component is reused, but if the architects don’t take responsibility for monitoring the component, they’ll deviate from it. The architects, and the company, own the service catalog.