VMware vSphere® uses the power of virtualization to transform data centers into simplified cloud computing infrastructures, enabling IT organizations to deliver flexible and reliable IT services.
The two core components of vSphere are VMware ESXi™ and VMware vCenter Server®. ESXi is the hypervisor on which you create and run virtual machines. vCenter Server is a service that acts as a central administrator for ESXi hosts that are connected on a network. With vCenter Server, you can pool and manage the resources of multiple hosts. vCenter Server allows you to monitor and manage your physical and virtual infrastructure.
Additional vSphere components are available as plugins that extend the functionality of the vSphere product.