A literature review is a systematic review of the published literature on a specific topic or research question designed to analyze-- not just summarize-- scholarly writings that are related directly to your research question.  That is, it represents the literature that provides background information on your topic and shows a correspondence between those writings and your research question.  This guide is designed to be a general resource for those completing a literature review in their field. 

Keep in mind that a literature review defines and sets the stage for your later research.  While you may take the same steps in researching your literature review, your literature review is not:

• Not an annotated bibliography in which you summarize each article that you have reviewed.  A lit review goes beyond basic summarizing to focus on the critical analysis of the reviewed works and their relationship to your research question.
• Not a research paper where you select resources to support one side of an issue versus another.  A lit review should explain and consider all sides of an argument in order to avoid bias, and areas of agreement and disagreement should be highlighted.

A literature review is important because it:

• Explains the background of research on a topic.
• Demonstrates why a topic is significant to a subject area.
• Helps focus your own research questions or problems
• Discovers relationships between research studies/ideas.
• Suggests unexplored ideas or populations
• Identifies major themes, concepts, and researchers on a topic.
• Tests assumptions; may help counter preconceived ideas and remove unconscious bias.
• Identifies critical gaps, points of disagreement, or potentially flawed methodology or theoretical approaches.
• Indicates potential directions for future research.

Thanks Dave Kellett   http://www.sheldoncomics.com/archive/100806.html