In a research paper, you use the literature as a foundation and as support for a new insight that you contribute.
The focus of a literature review, however, is to summarize and synthesize the arguments and ideas of others without adding new contributions.
The bibliography or reference section of sources you’ve already read are also excellent entry points into your own research.
There are hundreds or even thousands of articles and books on most areas of study.
The narrower your topic, the easier it will be to limit the number of sources you need to read in order to get a good survey of the material.
Your instructor will probably not expect you to read everything that’s out there on the topic, but you’ll make your job easier if you first limit your scope.
Literature reviews are written occasionally in the humanities, but mostly in the sciences and social sciences; in experiment and lab reports, they constitute a section of the paper.
Sometimes a literature review is written as a paper in itself.
In the sciences, for instance, treatments for medical problems are constantly changing according to the latest studies. However, if you are writing a review in the humanities, history, or social sciences, a survey of the history of the literature may be what is needed, because what is important is how perspectives have changed through the years or within a certain time period.
Try sorting through some other current bibliographies or literature reviews in the field to get a sense of what your discipline expects.