A literature review surveys scholarly articles, books and other sources (e.g. dissertations, conference proceedings) relevant to a particular issue, area of research, or theory, providing a description, summary, and critical evaluation of each work. The purpose is to offer an overview of significant literature published on a topic. For further information, take a look at the California State University, Chico's guide to literature reviews.
A good literature review will be well focused on the specific research question. The sources used will be currrent, relevant, authoratative, accurate, and from an unbiased perspective.
For a social science example, look at The role of justice and social exchange relationships in workplace deviance: Test of a mediated model from Human Relations.
For a biology example: Assisted colonization: Integrating conservation strategies in the face of climate change.