Literature reviews are usually done for 2 reasons. First you will often need a review to plan primary research, for instance to write a scholarly paper or article, this can be a journal article, or a longer paper like a thesis or dissertation. In this sense the literature review is the starting point or framework for a larger body of work. Literature reviews for primary research must have a rationale behind them.
Such rationales often include:
1. Lack of consistency in prior research
2. Flaws you think exist in prior research
3. Research that is addressed on a different population
4. Research that address innovations in a field that extends current research
5. Uncertainty about the interpretation of prior research
Second, a literature review can be an end in itself, for example you may review literature on a topic to write a grant proposal, perform planning or benchmarking for a program, or develop requirements for a project in your work.
