vCenter Lookup Service is a component of vCenter Single Sign On. Lookup Service registers the location of vSphere components so they can securely find and communicate with each other.

The vCenter Single Sign-On installer also deploys the VMware Lookup Service on the host. The Lookup Service enables different components of vSphere to find one another in a secure way. When you install vSphere components after vCenter Single Sign-On, you must provide the Lookup Service URL. The Inventory Service and the vCenter Server installers ask for the Lookup Service URL and then contact the Lookup Service to find vCenter Single Sign-On. After installation, the Inventory Service and vCenter Server are registered in Lookup Service so other vSphere components, like the vSphere Web Client, can find them.