How can virtual machines be characterized?

Virtual machines can be characterized as copies of real machines because they emulate the functionalities of physical hardware within a software environment. They allow multiple operating systems to run on a single physical machine, each isolated from the others, effectively behaving as if they are independent physical computers. This virtualization process means a physical machine's resources—like CPU, memory, and storage—are abstracted and allocated to virtual machines as needed.

In contrast, the other options do not accurately capture the essence of virtual machines. They are not physical servers, as they exist purely as software constructs, nor are they distinct network devices, as they rely on the infrastructure provided by the host server to operate on a network. Additionally, while virtual machines can utilize data storage, they are not primarily defined by their storage capabilities, but rather by their ability to simulate a separate operating environment.