Light Virtualization (LV in short) is a relatively new software technology. LV's approach is quite different to that of full virtualization, which requires a host system with virtual machine (VM) software installed in order to run emulated operating systems.
One of the main disadvantages of full virtualization has always been the lack of support for certain hardware devices like video cards. When running virtualized operating systems, users had to put up with emulated hardware, with all the limitations this would entail. For example, users could not run graphically demanding applications within an emulated operating system.
This has recently changed with the introduction of Intel's Virtualization Technology for Directed I/O (VT-d). With VT-d support, virtual machines are now able to access the host machine's hardware directly. The downside to this is that users will need VT-d capable hardware and a relatively powerful host system with a generous helping of RAM, in order to make the most of this technology.
In the case of LV there is no such need for special hardware or for a host system and VM software. The real system is being virtualized and you don't need a powerful system with lots of resources either: Light virtualization works well even on older and less powerful systems. When LV software is installed and activated, there is no need to start repairing when bad things happen. Things like most malware infections, installations of bad programs that mess-up the computer's settings, user configuration errors, even file system errors caused by crashes, all those things are reversible with just a simple computer restart.
So, how does this technology work? LV programs employ a virtualization buffer which is a reserved area that is totally isolated from the rest of the system. Once LV protection has been activated all system changes are contained strictly within that buffer and nothing touches the real system. This buffer is in most cases located on the protected disk. There are some LV programs that can also use RAM for the buffer, with all the speed and security benefits this entails.
Some LV applications are able to protect only the system partition/disk - the one that holds the operating system and is normally designated as C: - whereas others can protect all disks attached to the system, including USB sticks. Some of them work at file system level, with the virtualization buffer itself existing as a file that resides on each one of the protected volumes. Some others work at disk sector level and use the protected disk's free space for the virtualization buffer. This second approach is generally deemed as more secure among fans of such software.
When LV protection is active users have two choices when rebooting. Restart the system without committing any changes that have happened since LV protection was activated. In this case all changes that have happened on any protected disks/partitions will be discarded by default and those disks/partitions will be reverted back to their previous clean state upon reboot.
Commit all changes that have happened since LV protection was activated, and then restart. In this case all changes that have happened on any protected disks/partitions will be committed to those disks/partitions upon reboot. Please note that not all LV software offer such an option to commit changes. Some of them are designed to keep your disks/partitions unchanged no matter what, and as a result they offer no option to commit changes.
The basic concept of Light Virtualization is described visually in the following picture: