[My deepest apologies for not being on in a while and not contributing!]
Spirits are all around us, whether in the physical or in the astral plane. You can work with them in your spellcasting, which is called Spirit Work, or you may have a spirit guide and a spirit companion to do the same, which is to help you in your spellcasting. The only major difference is that your spirit guide helps you on your path, makes sure you don't stray away.
So, how does one understand these spirits that roam around us?
That is the question I will try to answer for you all.
First of all, spirits are to be respected. We humans are spirits too, but, we are spirits within a body, not a body within a spirit. We, as the spirits with a body, are to respect our kind that don't have a body, but used to. Respect and be respected.
I find it funny that a spirit can think it can control a spirit. I also find it disgusting. Spirits are not your slaves, they are not your toys. They are not your playthings. They are here to help you, to guide you, to show you. If you think you can use then as your little toys and try to control them, then by the Goddess, spirit work is absolutely not for you.
Now, I do not know much about demons, and quite frankly I really don't know how to research them. But, what I do know is not all of them are bad. They are cunning, I know, and they may use you, but not all are bad. You just have to know which you are dealing with. You must know how to protect yourself from the ones that are not too friendly as well.
I have heard this line all too many times: "If you have to ask about summoning a spirit, then you are not ready to." and I completely agree. Do your research before you try to summon a spirit, especially demons. You are not ready to summon if you know nothing about the spirit you wish to summon.
Please do your research about spirits in general to fully understand them.
I know that all of what I said here is not a full understanding of spirits, but, is there no point in trying?