About Virtual Machines
To add Windows or another operating system to your Mac, Parallels Desktop creates a "virtual machine," or a virtual computer, inside your Mac. You can then install Windows in the virtual machine, just as you would install an operating system on a regular computer.
Many use Parallels Desktop to create one virtual machine and install Windows in it. But you can install as many virtual machines as you like, and install a different operating system in each of them. That way you can use multiple operating systems together at the same time on your Mac. And just like with a regular computer, you can turn virtual machines on and off, configure them, and install and use applications.