Though not exactly a new concept, archetypes were perhaps best defined by Carl Jung, a Swiss psychologist and psychiatrist, and once pupil of Sigmund Freud. Ask a thousand people to describe something and you will get a thousand different responses, depending on the experiences and beliefs of the individual. The interpretation of God, for instance, will vary from person to person and at no time will you have two identical responses to an inquiry into the nature of God.
According to Jung, the true essence of a thing is essentially unknowable and indefinable. Perhaps the underlying nature of all abstract objects is energy. There is a substance that is all together unknowable; we ascribe meaning to this substance, according to our limited experiences and ideology. The indescribable substance would be the archetype, while the layers of meaning we use to define this would be what Jung called "complexes".