the iD, ego & superego

Our personality is made of up of three main interacting systems:

id:  

This is present at birth.  The id operates according to the pleasure principle i.e. it seeks pleasure and avoids pain.  It is our instinct.  If we want to do a particular thing we will do it.  for example, if we are in a lesson and we want to go to sleep, we go to sleep.

ego: 

The ego has to decide between the demands  of the id and the superego.  It operates according to the reality principle.   It controls the id's drive for immediate satisfaction until an appropriate outlet can be found.  So, from the example of the id,  above, the ego would say there is no bed here but I could lay on the table. 

superego: 

the superego develops from the oedipus complex. This is the moral part of the personality; a product of socialisation.  the super ego is divided into two parts; the ego-ideal and the conscience.  the ego-ideal is the standards of good behaviour that we aspire to.  the conscience is seen as an "inner voice" that tells us when we have done something wrong.  depending on whether the ego-ideal or conscience is activated, The superego is seen as the source of rewards i.e. feelings of pride and satisfaction and of punishments i.e. feelings of shame or guilt, respectively.  So again, continuing with the same example, your superego would say that you cannot possibly go to sleep in a middle of a lesson.

The demands of the id ('I want it, I want it now') and the demands of the superego ('no it's wrong') frequently conflict.  The ego deals with this conflict by operating unconscious defence mechanisms.