Sometimes the terms emulator and simulator are used to distinguish between two different types of software.

An emulator emulates the hardware (CPU, network interface, disk, graphics, etc.) and the real operating system runs mostly or entirely unmodified atop this.

A simulator reproduces the APIs that an application expects without running the actual operating system code, through some combination of a port or a reimplementation.

However, I think it's fair to use the word simulation here too. It is a simulation from the user's point of view.

In fact, another way to categorize all this is at which level the mimicry happens: hardware, API, or user.