VirtualBox is a hosted hypervisor, which means it runs as an application on top of an existing operating system, not as a special kernel that is booted before the first regular operating system starts1. VirtualBox supports a large number of guest operating systems, including Windows, Linux, Solaris, OS/2, and OpenBSD1. VirtualBox does not require dedicated shared storage, as it can store virtual machine disk images locally on block devices of the virtualization host, or on network shares, or on iSCSI targets1. VirtualBox provides both a graphical user interface (GUI) and command line tools (VBoxManage) to administer virtual machines1. VirtualBox is available for Windows, Linux, macOS, and Solaris hosts1, and does not require the source code of the currently running Linux kernel to be available. References:

Oracle VM VirtualBox: Features Overview