What is the difference between fallen angels, demons, unclean spirits, and familiar spirits?

What is the difference between fallen angels, demons, unclean spirits, and familiar spirits?
 
This is a matter concerning which many seek to be wise beyond what is written, with results that are not profitable, either to themselves or to others. That Satan is a fallen angel, and a leader of other angels who fell with him, just as Michael is of unfallen angels, seems to be definitely proved by Revelation 12:7. That the sinning angels of 2 Peter 2:4 and Jude 1:6 are a different company, whose fall took place at a different time, is a view held by some, but without sufficient proof. That Satan is identical With Beelzebub the prince of demons is implied in Matthew 12:24-28 and Mark 3:22-26, where Christ uses the terms interchangeably; and if that be so, the demons are most probably of the number of those who fell with him. These demons are otherwise called “unclean spirits,” because of their character, as may be seen by comparing verses Mark 5:12 and 13.  As for “familiar spirit,” it is a term used in the Old Testament of demons who, by entering into diviners, enabled them to carry on their evil work. See 1 Samuel 28:7, etc.. The “spirit of divination” in the damsel of Acts 16:16 is similar. W.R.