A literature review identifies the major source texts in your area and briefly summarises their arguments. It is a way of showing the ideas that already exist in areas that relate to your chosen topic. It also shows how those ideas can help you put your subject into a context, and show why it is a worthwhile academic investigation. Your dissertation will be anchored in these texts and the arguments they forward. The purpose of a literature review is to provide a critical and informed background for your thesis research.