Disclaimer
A virtual machine is a software computer that, like a physical computer, runs an operating system and applications. The virtual machine consists of a set of specification and configuration files and is backed by the physical resources of a host. Every virtual machine has virtual devices that provide the same functionality as physical hardware but are more portable, more secure, and easier to manage.
You can create and deploy virtual machines into your data center in several ways. You can create a single virtual machine and install a guest operating system and VMware Tools on it. You can clone or create a template from an existing virtual machine, or deploy OVF templates.
Virtual machines typically have an operating system, VMware Tools, and virtual resources and hardware that you manage in much the same way as you would manage a physical computer. You install a guest operating system on a virtual machine the same way as you install an operating system on a physical computer. You must have a CD/DVD-ROM or ISO image containing the installation files from an operating system vendor.
Virtual Machine Files
More Explanation
Additional files are created when you perform certain tasks with the virtual machine.