Figure 2
From: Software platform virtualization in chemistry research and university teaching
The virtual machine software installed on a host operating system allows the use of different operating systems on a single computer system. A Macintosh system could run native Windows or LINUX software or even multiple instances of the same operating system. All virtual machines can communicate with each other and are allowed to use all hardware computer resources such as graphic cards, DVD drives and USB ports. (Logo sources: Wikipedia, TUX mascot: Larry Ewing).