A literature review, a literature survey, a state of the art is an extended write-up collecting, and often comparing and commenting on a set of publications addressing a specific topic/question.
Their main purpose is not to present original research, nor serve as teaching material, but to provide a gateway to the latest and/or most valuable research on a particular topic. This can serve to jumpstart a bibliography, as a first chapter of a dissertation, or to guide newcomers to a field where textbooks aren't available, or too broad or too dated.
Note the three terms are not synonymous but gather well under the same tag.
See also: , .