The Ego is merely a "mental concept" by Sigmund Freud to explain "desire", or "ambition". The Id is the the basic instincts we are born with. The Super-ego, or "conscience" is what controls the other two from being "out of control". The basic instinct when we "desire" something is to take it; steal! The super-ego tries to stop us from doing it.
The basic instinct of a man is to have sex with as many females as possible. The super-ego tells him that's a bad idea!
You should read "The Ego And The Id", by Sigmund Freud. He coined both words!