Snapshot function in Virtualbox (backup many status of os)

Virtualbox is a free, opensource virtual pc software. Beside Virtualbox, we can use many other free softwares like qemu, vmware player ... but i think virtualbox is the best because it is nice, power, can connect with gns3 to simulate network systems (qemu can still connect but not power like virtualbox).
In the simplest way, we use Virtual pc software with an iso image file of an operating system to install and run the operating system (OS) in a window to test or run certain tools that the operating system on pc / laptop does not currently do. But virtual pc softwares have many more powerful functions than it and Snapshot is one.
With a real pc/laptop, I use softwares like norton ghost, true image ... to backup OS. I must restart PC with a boot pc and configure to backup to an image file. I need about near half of hour for each time.
With virtualbox, before, I can backup file vdi by compress this to a archive file. I really happy with each time, I only need back in less than ten minutes.
But, with snapshot, I can do them with < one minutes, can backup in running, save memory, and can struct in a tree to manager snapshots.

To use it, we need click snapshot button (blue arrow)
Create snapshot (red arrow), we can do it when virtual pc is running.
And can clone this state to other virtual pc with button in black arror.
Choose status you want to restore, and click restore button near create button.

Very easy,  very powerful. When i try softwares, special in linux (hard to install softwares), this function help me very good.