I would like to add more to this, firstly dream can be defined as a thought or image or even imagination which appears in someone's mind when sleeping and also nightmares on the other hand is just a bad dream so the two are somehow connected, most times it's almost difficult to understand the dreams we have in our sleep the reason being that dream cannot be exactly as what it's all to be in the real life so it takes a talent or grace for someone to explain what a dream means