Or, it could be defined as the opposite:

An emulation presents a replica of something else's outward observable behavior.

A simulation runs a specific internal model, which generates some gestalt behavioral results.

An emulator might simply mimic surface-level behavior directly, or use an internal simulation in order to generate it from first principles.

There really isn't a hard and fast agreed-upon definition of these terms in software, but these seem in tune with their non-computing definitions.