VirtualBox – Best free and open-source virtual machine software

VirtualBox (formerly called Sun VirtualBox, Sun xVM VirtualBox and Innotek VirtualBox, now its full name should be Oracle VM VirtualBox) is a powerful cross-platform, open-source and x86-based virtual machine (VM) software. It allows users to virtual other x86-based operating systems on 32-bit or 64-bit Windows, Solaris and Linux operating systems, that is to say, the user can install and run Solaris, Windows, DOS, Linux, OS/2 Warp, OpenBSD or FreeBSD system as the client operating system in VirtualBox.