The traditional approach to Identity is Essentialism, this is basically our biological make-up - we are born with it in our genes, however this approach allows a lot of stereotypes and cliches. When looking at the historical phases of identity it tends to be that within pre-modern times, identity was stable; the modern age, there was more of a choice, there was a wider range of social roles and within post-modern this is where identity is created and constructed by ourselves and not determined by another.
There are many writers on Identity and each had their own view on the subject. Baudelair spoke of the gentleman-stroller as an identity how they would show themselves off within society. Simmel spoke of the Trickle Down theory where people would hide behind what they wore. Whatever the upper class wore, would trickle down into society and soon enough the lower class would wear similar clothing to try and fit in, but obviously at a lower standard. It was and endless cycle of wearing something new to distinguish social standing.
Foucault introduced the Discourse Analysis where identity is constructed out of the discourses e.g. age, class, gender, sexual orientation, race/ethnicity, nationality. If you take class and look at the work of photographer Martin Parr - Ascot 2003 it could be suggested that is he making a social comment on class and the people trying to pursue a different identity. Are they upper class by just attending Ascot and dressing in a very formal matter? Under gender and sexuality the fashion industry where it is mainly targeted towards women, is actually the work of men.
The postmodern identity is constructed through our own social experience. We have the option of inventing our own identity, it is not something that has to be discovered. We have the means of technology to create our own identities in the form of social networks or within a virtual reality like Second Life. Virtual worlds provide environments for experiences however it can be an artificial representation of who the person really is. There are no boundaries within the virtual world, you can be whoever you want to be and this can actually lead to an alienation, a bleak life. People may end up living a lie, constructing a fake life and living it within a virtual world. To some people it's probably easier becoming who you want to be in that world than in real life. It is a form of escape.