The meaning of social identity is a persons sense of who they are based on their group membership and gives us a sense of belonging in the social world.

Henri Tajfel and John Turner proposed a Social Identity Theory as a way to explain intergroup behaviour.Also that the groups we belong to are important source of pride and self-esteem, there is in-group(us)and out-group(them).There are three mental stages involved in evaluating others:

Categorization-We categorize people in order to understand the social environment.

Social Identification-We adopt the identity of the group we have categorized ourselves as belonging to and this defines who you are. We also give identify other certain social groups in the way they dress and act.

Social Comparison-Once we have categorized ourselves as a part of a group and identified with that group,in order to increase our self image the in-group will discriminate against the out-group. 

                                                                Mods v.s Rockers

One main examples for this theory is Mods and Rockers.These were two conflicting sub-cultures of the early 60s-70s in Britain.The Rocker subculture was centred on motorcycling and this was represented in the way they dress e.g.black leather jacket.Music was another main influence in the way they acted and dressed,Rockers listened to Rock and roll.However the Mod subculture was centred around fashion and music,Mods wore suits and a much more clean-cut outfit compared to Rockers.They mainly listened to soul and blues.They are two very different subcultures meaning a lot of conflicts and fights due to them discriminating each other to make their social group look better.