http://www.vmware.com/support/ws55/doc/glossary_ws.html#wp1018930

Physical disk

— A hard disk in a virtual machine that is mapped to a physical disk drive or a partition of a drive on the host machine. A physical disk is also referred to as a raw disk. A virtual machine’s disk can be stored as a file on the host file system (see Virtual disk) or on a local hard disk. When a virtual machine is configured to use a physical disk,VMware Workstation directly accesses the local disk or partition as a physical device (not as a file on a file system). It is possible to boot a prevIoUsly installed operating system on an existing partition within a virtual machine environment. The only limitation is that the existing partition must reside on a local IDE or SCSI drive.