the Jester
Legend
Well. From what I understand, "Demon" is just "Fallen angel", "evil spirit" or basically "Inhabitant of Hell" and "Devil" has only been used to refer to the individual in charge of hell: Satan, Lucifer, etc.
Not entirely true- there have long been a variety of 'devils' in parlance, some of which are sort of pseudopersonifications of a perceived evil, such as the blue devil alcohol.