The following definition is taken from Wikipedia.org Here.

In computing, Desktop Virtualization involves separating the physical location where the PC desktop resides from where the user is accessing the PC. A remotely accessed PC is typically either located at home, at the office, or in a data center. The user is located elsewhere, perhaps traveling, in a hotel room, at an airport, or in a different city. The desktop virtualization approach can be contrasted with a traditional local PC desktop, where the user directly accesses the desktop operating system and all of its peripherals physically (using the local keyboard, mouse and video monitor hardware directly).

When a desktop is virtualized, its keyboard, mouse and video display (among other things) are typically redirected across a network via a desktop remoting protocol (such as RDP, ICA, VNC, etc). The network connection carrying this virtualized desktop information is known as a “desktop access session.”

Virtually any kind of end-user device can be used to remotely access a virtualized PC desktop, including thin clients, notebook PCs and even a PDA. Once a desktop is virtualized, it becomes accessible over any suitable network connection, on any device with similar characteristics.