Spoon uses proprietary app virtualization technology to allow streamed apps to execute instantly in an isolated environment on any Windows desktop. Unlike hardware virtualization solutions such as VMware and Virtual PC, which emulate the underlying hardware and therefore require an entire copy of the host operating system, Spoon app virtualization technology emulates operating system features required for execution. As a result, Spoon virtual apps have essentially the same performance characteristics as native executables.
The core of Spoon app virtualization technology is the Spoon virtual machine (VM) kernel. The Spoon kernel is a lightweight implementation of core operating system APIs, including the filesystem, registry, process, and threading subsystems, completely implemented within the user-mode space, allowing Spoon apps to be executed without any device driver installation or administrative privileges.
Apps executing within the Spoon virtual environment interact with a virtualized filesystem, registry, and process environment, rather than directly with the host device operating system. The virtualization engine handles requests within the virtualized environment internally or, when appropriate, routes requests to the host device filesystem and registry, possibly redirecting or overriding requests as determined by the app configuration:
This is a cool technology, instead of virtualizing the entire computer hardware, this allows virtualizing only the parts needed by individual applications, that combined with a streaming technology allow you to run for e.g. multiple browser versions in the cloud.
[Update] This is actually cooler than I thought, I ran FF 4 beta using spoon and realized that the browser is actually running on my machine and not on the cloud, because when I goto open or save files, it shows the location as being my computer. Awesome!