That is an oversimplified question. Many possibilities exist. For instance.
Is it in a slide?
Is the frame complete or partial?
Did the manufacturer hide juctions for electrical wires underneath it. Is there equipment mounted under it? This can include slide motors, pumps, or a number of other things.
It is possible that a wheel well is there and the sofa is just good use of space.
You will need to get your hands dirty for proper assessment.