A literature review summarizes the scholarly research that is available about a specific topic. Scholarly research can be articles, books, gray literature, and more. 

Through a literature review, you may discover that there is a gap in the literature -- this leads to your research question or project. 

To support your research project, you will want to find good evidence-based research. Types of publications and methodology contribute to the level of evidence. Below are basic representations of the evidence pyramid. But your literature review will contain more than just EBP research.