Yeshua makes it clearer in the book of Revelations mentioning all of them within one verse:
Revelation 12:9 (KJV) And the great dragon was cast out, that old serpent, called the Devil, and Satan, which deceiveth the whole world: he was cast out into the earth, and his angels were cast out with him.
So Satan is also known as the Devil to people and he has his own band of angels that follow him. It is mentioned in the book of Enoch that the number that fell away from God was 1/3. Satan wanting to be God and replace God to be worshipped. Are they spirits? Yes but angels are also called messengers of God, so Satan mimics God and has his own messengers.
Yeshua also mentions so is surrounded by devils and spells out that there is no truth in them, He even called us evil that I went into on another post. Yet a description is here:
John 8:44 (KJV) Ye are of your father the devil, and the lusts of your father ye will do. He was a murderer from the beginning, and abode not in the truth, because there is no truth in him. When he speaketh a lie, he speaketh of his own: for he is a liar, and the father of it.
The other thing this makes me wonder, is, are we doing properly in casting out devils, people bind Satan and cast him out usually but are all demons meaning those fallen angels with him called Satan? As I recall Yeshua asked and found one full of evil spirits and the name was Legion. Also, the word for devils that Yeshua said to cast out are spirits that is the meaning of that particular word.
Searching the scriptures for ourselves cause us to wonder about all that is just taught and accepted. Heck most churches don't even bind Satan in a service let alone cast out devils or even use the term. Then we wonder why we don't see miracles from God, are we following instructions? Some give up and not search for understanding sometimes for me anyway when the Lord said "look up" I think it might have been to look up words not just seeing the sky and not just to make you feel good.In Greek: a dæmonic being; by extension a deity:—devil, god. and in Hebrew: a dæmon or supernatural spirit (of a bad nature):—devil.