What is a virtual machine (VM)?

A virtual machine (VM) is best defined as an isolated environment on a physical machine. This environment operates as if it were a separate computer, complete with its own operating system and applications. VMs are created by virtualization software, which allows multiple instances of operating systems to run on a single physical hardware system, effectively sharing the underlying resources such as CPU, memory, and storage.

The key aspect of a VM is that it provides isolation, enabling different operating systems and applications to run independently of each other on the same physical hardware. This is particularly useful for testing, development, and server consolidation, as it allows users to run various configurations without needing multiple physical machines.

While some other choices mention components or tools, they misrepresent the nature and function of a virtual machine. A VM is not a physical hardware component; it relies on a host machine for resources, and it is not a physical storage device or purely a network security tool. Instead, its primary purpose is to create virtual environments that simulate the functions of an actual computer, thereby enhancing flexibility and efficiency in resource usage.