A literature review discusses published information in a particular subject area, and sometimes information in a particular subject area within a certain time period.
A literature review can be just a simple summary of the sources, but it usually has an organizational pattern and combines both summary and synthesis. A summary is a recap of the important information of the source, but a synthesis is a re-organization, or a reshuffling, of that information. It might give a new interpretation of old material or combine new with old interpretations. Or it might trace the intellectual progression of the field, including major debates. And depending on the situation, the literature review may evaluate the sources and advise the reader on the most pertinent or relevant.
This University of North Carolina at Chapel Hill site provides a thorough overview of what exactly a LitReview is, and what it is NOT.
How to write a literature review.
This University of Wisconsin-Madison site provides you with information on how to write the Introduction, Body, and Conclusion portions of your LitReview. It also provides several sample LitReviews as examples.