A Literature review is a body of text that aims to review the critical points of current knowledge on a particular topic.
Most often associated with science-oriented literature, such as a thesis, the literature review usually precedes a research proposal, methodology and results section. Its ultimate goal is to bring the reader up to date with current literature on a topic and forms the basis for another goal, such as the justification for future research in the area.
A good literature review is characterised by: a logical flow of ideas; current and relevant references with consistent, appropriate referencing style; proper use of terminology; and an unbiassed and comprehensive view on the topic.
According to Cooper (1988) "a literature review uses as its database reports of primary or original scholarship, and does not report new primary scholarship itself. The primary reports used in the literature may be verbal, but in the vast majority of cases reports are written documents. The types of scholarship may be empirical, theoretical, critical/analytic, or methodological in nature. Second a literature review seeks to describe, summarise, evaluate, clarify and/or integrate the content of primary reports".
Source: Cooper, H.M. (1988): The structure of knowledge synthesis - Knowledge in Society, vol. 1, pp, 104-126.
reference to wikipedia
http://en.wikipedia.org/wiki/Literature_review
here is another website that teach you what exactly it is
http://www.languages.ait.ac.th/EL21LIT.HTM