As you already know, vCenter enables centralized management of your core vSphere infrastructure. In large environments there can be more than one vCenter server deployed to manage the resources, it is beneficial to view all the vCenter inventories from a single management plane. This can be achieved using Enhanced Linked Mode.
Enhanced Linked Mode enables the linking of more than one vCenter Server, be it vCenter installed on a Windows machine or the VCSA. Although it is referred to as a method to link vCenter servers together, the actual linking happens between the Platform Service Controllers the vCenters are connected to. It is done so by making the PSCs join a single SSO domain. This is a requirement. The PSCs in the same SSO domain will replicate roles and permissions, licenses, and other details letting the administrator perform a single login into the vSphere Web Client to view and manage inventory objects of all the linked vCenter servers.