Your body is your flesh, blood, bone, and all that good stuff. Your spirit is just like your body, only in the next demension. Demons and Angels fall in that category. Call it the 4th demension. Spirits can interact with each other just like bodies can here. They follow rules and laws just like in every other aspect of life. Your soul is your mind, will, and emotions. It isn't tangible. Death is when your spirit and soul separate from your body.
Biblically speaking.
Or we are simply an act of random mathematics.