vCenter Server is a service that centralizes the management of the ESXi hosts and the VM that run on the hypervisor. This vSphere core component not only interacts with ESXi hypervisors, but also integrates with other VMware products—vRealize Automation, Site Recovery Manager, and vSphere Update Manager, to give you some examples.

vCenter Server is not limited to act as a central management tool. The advanced features such as a sign-on server (SSO), centralized authentication, vMotion, DRS, HA, and FT are all services that come into play only when vCenter Server is present in the infrastructure. With vCenter Server, you can manage resources, ESXi hosts, VM, templates, logs and stats, alarms and events, and so on. Besides, vCenter Server provides all the functionalities needed to distribute and manage the network services, ensuring the availability of resources and data protection. 

Starting from vSphere 6.0, the vCenter installation includes the deployment of two components:

• Platform Service Controller
• vCenter Server