A literature review evaluates the existing scholarly research in a given topic. A literature review goes beyond a summary of the literature; it explains the relationship between previous studies and how they are related to your research.
Bourner (1996) stated that prior starting a research project one has to review the literature. He also provided the following reasons for conductiong a literature review:
Bourner, T. (1996) The research process: four steps to success. In T. Greenfield (Ed.), Research methods: guidance for postgraduates (pp.7-11). London: Arnold.