Submitted by Mi-K on Monday, September 24, 2012 - 3:27pm
VirtualBox is a virtualization manager that enables to add different OS on other OS.
Let's admit you have a PC with Windows 7 installed. In the past, if you wanted to have a Linux, you were obliged to install it like any OS with a DVD and boot on it.
And then, reboot each time you wanted to use one of them.