(1) A thin client architecture in which each user's desktop, which includes the operating system and applications, runs in a separated "virtual machine" partition in a server on the network. Commonly called "virtual desktop infrastructure" (VDI), the desktop is delivered over the network in real time to the user's PC, which functions only as an input/output (I/O) terminal. The data processing is performed in the server. Sometimes called "client virtualization," although the desktop virtualization definition in #2 below is a more viable description of client virtualization. See thin client and virtual machine.
(2) A virtualized environment in the user's machine. Also called "client virtualization" and "endpoint virtualization," the user's computer hosts multiple virtual machines, each of which contains an operating system and set of applications. See client-side hypervisor, virtual machine, Virtual PC, Parallels Desktop and VMWare Fusion.
(3) A thin client architecture in which a central server timeshares desktops to multiple users. More precisely called "shared sessions," Microsoft's Terminal Services, the terminal services function in Microsoft's Remote Desktop Services and Citrix XenApp, are examples of products that use this approach. See thin client, Terminal Services and Remote Desktop Services.