A collection of virtual hardware that creates a standard x86 or x64 enviornment that allows for the installation of a supported guest operating system.

A virtual machine is a software computer that, like a physical computer, runs an operating system and applications. The virtual machine is comprised 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 and have additional benefits in terms of portability, manageability, and security.

A virtual machine consists of several types of files that you store on a supported storage device. The key files that make up a virtual machine are the configuration file, virtual disk file, NVRAM setting file, and the log file. You configure virtual machine settings through the vSphere Web Client or the vSphere Client. You do not need to touch the key files.

A virtual machine can have more files if one or more snapshots exist or if you add Raw Device Mappings (RDMs).

Other Definition:

A virtual machine (VM) is a software implementation of a computing environment in which an operating system (OS) or program can be installed and run.

The virtual machine typically emulates a physical computing environment, but requests for CPU, memory, hard disk, network and other hardware resources are managed by a virtualization layer which translates these requests to the underlying physical hardware.

VMs are created within a virtualization layer, such as a hypervisor or a virtualization platform that runs on top of a client or server operating system. This operating system is known as the host OS. The virtualization layer can be used to create many individual, isolated VM environments.

Typically, guest operating systems and programs are not aware that they are running on a virtual platform and, as long as the VM’s virtual platform is supported, this software can be installed in the same way it would be deployed to physical server hardware. For example, the guest OS might appear to have a physical hard disk attached to it, but actual I/O requests are translated by the virtualization layer so they actually occur against a file that is accessible by the host OS.