Freud Theroy

The Id, Superego, ego is a psychoanalytical theory created by Sigmund Freud, an Austrian neurologist (1856-1939). This theory is the idea that both consciously and subconsciously we are controlled by three aspects of our minds, the id, the super ego and the ego. 
The id is the disorganized part of the personality structure that contains a human's basic, instinctual drives, it is also the only aspect of the mind that is present from birth. It is also the source of our bodily needs, wants, desires, and impulses, particularly our sexual and aggressive drives. The id has no concept of self restriction, socially acceptable actions and rules and regulations of the world around it, It only wants. A representation of this would be a new born baby. A babies only instinct is to fulfil its spontaneous needs and wants, it has no awareness of the world around him, it only craves its own intrinsic needs 
the super ego is the polar opposite to the ego, it is the part of our consciousness that incorporates the values and morals of society which are learned from our parents and those around us. The superego's purpose is to control and essentially repress the ID, especially the primal human urges such as sex, aggression and want. it also houses the purpose of attempting to persuade the ego to turn to a more moralistic, society acceptable goal rather than the ID's primal urges and to strive for perfection. 
the ego on the other hand is the aspect of the mind that sits perfectly in-between both the superego and the ID, it the aspect of the brain that essentially makes physical decisions within the physical world. this isn't to say that the ego cannot be persuaded or challenged by the ID or the super ego. One would naturally find themselves naturally siding with the ego in terms of wants and needs of the physical form, but unlike the Id, the ego also considers social and cultural factors into is decision making, upon which it relies on the superego to communicate how to act upon the social and cultural factors around it. 
this theory can be perfectly represented with the chariot analogy, imagine two horses and a chariot racing down a road, it is the chariots duty ti guide and control the two horses pulling the chariot, the chariot cannot allow itself to favour either horse, unless it veers of the road, it has to keep both horses in reign, in order to allow itself to keep itself straight.