The Oxford Advanced Learner's Dictionary gives the following example phrase:
a fireplace with realistically glowing coals
I'd like to know why "realistically" is used in the first place. What difference would it make if it were removed?
It means that the fire in the fireplace is not real but almost looks like real. It might be something made from plastic with hidden light bulbs inside to make it glow through the plastic. But this "fake fire" is made so well that it looks realistic—like real coals that are glowing.
If "realistically" were removed, it would mean that this is a fireplace with real coals and real fire.