VirtualBox software enables you to run a guest OS inside your host OS. This is helpful if you need to utilize an OS that isn't currently installed on your computer to run a program or OS or if you want to try out an OS before installing it. VirtualBox supports various guest operating systems, from Windows and Linux to Mac OS X and even Solaris and FreeBSD. VirtualBox lets you customize the operating environment by altering settings like the virtual machine's RAM, CPU speed, and hard drive type.