VirtualBox
13 September 2013
VirtualBox is open source software for virtualization created by German company Innotek. Then it was sold to Oracle Corporation.
It can work on most popular modern operation systems: Windows, Linux, Mac OS X, FreeBSD, OS/2 Warp and other.
VirtualBox is installed on the existing operation system. Another operation system is installed inside VirtualBox. This operation system runs as separate virtual environment.