vSphere is an umbrella term for VMware's virtualization platform. The term vSphere encompasses several distinct products and technologies that work together to provide a complete infrastructure for virtualization. These products and technologies include the following:
ESXi: ESXi is the core of vSphere; it is a Type-1 hypervisor that runs on host computers to manage the execution of virtual machines, allocating resources to the virtual machines as needed. ESXi comes in two basic flavors:
Installable: The Installable version of software can be installed onto the hard drive on a host computer, much as any other operating system can be installed.
Embedded: The Embedded version runs as firmware that is actually built into the host computer. It's preinstalled into read-only memory by the manufacturer of the host computer.
vCenter Server: vCenter Server is a server application that runs on Windows Server installed in a virtual machine. vCenter is the central point for creating new virtual machines, starting and stopping virtual machines, and performing other management tasks in a vSphere environment.
vCenter Client: vCenter Client is a Windows application that you use to access the features of a vCenter Server remotely. vCenter Client is the tool you'll work with most when you manage a vSphere environment.
VMFS: VMFS, which stands for Virtual Machine File System, is the file system used by vSphere to manage disk resources that are made available to virtual machines. With VMFS, you can create data stores to access physical disk devices, and you can then create volumes on these data stores to make disk storage available to virtual machines.
