RemoteBox is a graphical utility that allows you to administer virtual machines running in VirtualBox over a network, either on a remote server or on a local machine. This allows you to remotely administer a server running VirtualBox and interact with the virtual machines as if they were running locally.
VirtualBox is installed on the "server" machine, and RemoteBox runs on the "client" machine. RemoteBox provides a full GTK graphical interface with a look and feel very similar to the built-in VirtualBox GUI.