The manner in which one perceives oneself. The Self-Concept is derived from several factors including: certain personality traits, how you look, your personal values and life goals, and your place or role in life. The Self-Concept is the way babies and children start to understand the social world in relation to themselves . Relationships with relatives and friends/mentors influence the developmental process heavily.
In childhood the Self-Concept tends to be tied to concrete or physical things like looks, items and skill levels. As the child grows, they learn about things like intrinsic (inner) characteristics and psychological differences due to the fact that they now have a larger network of peers and mentors to compare themselves with. Later in life (teenager-adulthood) the self-concept changes into a more nebulous idea that is organized by what is relevant to the individual.
Self-Concept is an everchanging concept depending on the person because our feelings, personal belief systems and attitude can change when new information is shown to us.