1.2. Some Terminology

When dealing with virtualization, and also for understanding the following chapters of this documentation, it helps to acquaint oneself with a bit of crucial terminology, especially the following terms:

  • Host operating system (host OS). This is the OS of the physical computer on which Oracle VM VirtualBox was installed. There are versions of Oracle VM VirtualBox for Windows, Mac OS X, Linux, and Oracle Solaris hosts. See Section 1.4, “Supported Host Operating Systems”.

    Most of the time, this manual discusses all Oracle VM VirtualBox versions together. There may be platform-specific differences which we will point out where appropriate.

  • Guest operating system (guest OS). This is the OS that is running inside the virtual machine. Theoretically, Oracle VM VirtualBox can run any x86 OS. such as DOS, Windows, OS/2, FreeBSD, and OpenBSD. But to achieve near-native performance of the guest code on your machine, we had to go through a lot of optimizations that are specific to certain OSes. So while your favorite OS may run as a guest, we officially support and optimize for a select few, which include the most common OSes.

    See Section 3.1, “Supported Guest Operating Systems”.

  • Virtual machine (VM). This is the special environment that Oracle VM VirtualBox creates for your guest OS while it is running. In other words, you run your guest OS in a VM. Normally, a VM will be shown as a window on your computer's desktop, but depending on which of the various frontends of Oracle VM VirtualBox you use, it can be displayed in full screen mode or remotely on another computer.

    In a more abstract way, internally, Oracle VM VirtualBox thinks of a VM as a set of parameters that determine its behavior. They include hardware settings, such as: how much memory the VM should have, what hard disks Oracle VM VirtualBox should virtualize through which container files, what CDs are mounted. They also include state information, such as: whether the VM is currently running, saved, if the VM has snapshots. These settings are mirrored in the VirtualBox Manager window, as well as the VBoxManage command. See Chapter 7, VBoxManage. In other words, a VM is also what you can see in its Settings dialog.

  • Guest Additions. This refers to special software packages which are shipped with Oracle VM VirtualBox but designed to be installed inside a VM to improve performance of the guest OS and to add extra features. See Chapter 4, Guest Additions.