Part of the definition of gender socialization involves the understanding of how social orders view the defining characteristic of gender. This includes how social orders "gear" gender orientation to certain ends. For example, when infant who is a girl is given dolls with which to play and a boy is given army figures, this is a subtle example of gender socialization for it is using social practices to gear an individual's perception of gender roles. In a high school, when girls are encouraged to to take cooking classes and boys auto shop, it is another form of gender socialization. In both of these settings, social expectations of gender impact decision making practice of individuals. It is gender that is used to define how once social activity is geared. This is a part of gender socialization.
Gender socialization refers to the learning of behaviour and attitudes considered appropriate for a given sex. Boys learn to be boys and girls learn to be girls. This 'learning' happens by way of many differents agents of socialization. Family is definitely important in enforcing their kid's gender role but so are their friends, school, work and the media. They're just trying to figure out who they are.