The term "literature review" has two meanings. One is the process of reviewing the publications, the articles, books, research reports, and dissertations relevant to a topic (this is "the literature") in order to find out about what has been done and what opportunities there are to add to the knowledge about a topic.
The other sense of literature review is the product of your search through the literature, your written review of the literature.
A literature review in the second sense as a product is a succint presentation of material that is relevant to your topic or area of research. A literature review often forms the intellectual groundwork on which you will build a case for something. The body of a literature review includes brief descriptions of and references to: articles, books, theses, research reports, or government documents.
Chris Hart, in the introduction to the book Doing a Literature Review (SAGE, 1998) describes the purpose of a literature review as being to:
Reviewing literature for research "...is important because without it you will not acquire an understanding of your topic, how it has been researched, and what the key issues are. In your written project you will be expected to show that you understand previous research on your topic. This amounts to showing that you have understood the main theories in the subject area and how they have been applied and developed, as well as the main criticisms that have been made of the work on the topic. The review is therefore a part of your academic development - of becoming an expert in the field."
The goal of a literature review should be "the use of the ideas in the literature to justify the particular approach to the topic, the selection of methods, and the demonstration that [your] research contributes something new." (page 1)
See also Using Scholarly Articles and Books as References
From The Literature Review: a Step-by-Step Guide for Students (Diana Ridley, London: SAGE Publications, 2008) and Doing a Literature Review (Chris Hart, London: SAGE Publications, 1998):