virtualbox.org

What's the difference between a VM specified as, say, DOS and a VM specified as Ubuntu? Is there any difference besides superficial things like what storage drives are used and how much memory and hard drive space is allocated by default? Would you be able to specify a VM as being of type Windows 7 and then install a Linux distro on it? (Not that there's any practical reason to do this; but it's the concept that matters.)

The logic behind it is to configure a hardware "recipe" for the vm which best suits the OS to be installed. As an example it will select a NIC driver which the OS has "out of the box". It will also emulate the chipset best suited to the OS (very important for older OSs).