In simple terms, a literature review investigates the available information on a certain topic. It may be only a knowledge survey with an intentional focus. However, it is often a well-organized examination of the existing research which evaluates each resource in a systematic way. Often a lit review will involve a series of inclusion/exclusion criteria or an assessment rubric which examines the research in-depth. Below are some interesting sources to consider.
Ten Simple Rules for Writing a Literature Review - This 
PLoS One article itemizes the steps in the lit review process.
The Writing Center's Literature Reviews - UNC-Chapel Hill's writing center explains some of the key criteria involved in doing a literature review.
Cochrane Handbook for Systematic Reviews of Interventions by There are methods of evidence synthesis that go beyond writing a general literature review. They are research studies in themselves. Systematic reviews and meta-analyses appear at the top levels of clinical evidence because they systematically analyze all of the available research to answer a clinical question. The methodologies for conducting this type of research will vary depending on whether the included studies were qualitative, quantitative, or mixed methods. There are strict guidelines for reporting and conducting most of these types of studies.
See the article cited below to explore review types:
Grant, M. J., & Booth, A. (2009). A typology of reviews: an analysis of 14 review types and associated methodologies. Health information and libraries journal, 26(2), 91–108. https://doi.org/10.1111/j.1471-1842.2009.00848.x
Barnett-Page, E., & Thomas, J. (2009). Methods for the synthesis of qualitative research: a critical review. BMC medical research methodology, 9, 59. https://doi.org/10.1186/1471-2288-9-59. Article link
Lockwood C, Porrit K, Munn Z, Rittenmeyer L, Salmond S, Bjerrum M, Loveday H, Carrier J, Stannard D. Chapter 2: Systematic reviews of qualitative evidence. In: Aromataris E, Munn Z (Editors). JBI Manual for Evidence Synthesis. JBI, 2020. Available from https://synthesismanual.jbi.global.
Sandelowski, Margarete & Barroso, Julie. (2003). Creating Metasummaries of Qualitative Findings. Nursing Research, 52(4), 226-233. Retrieved from http://ovidsp.ovid.com/ovidweb.cgi?T=JS&PAGE=reference&D=yrovftf&NEWS=N&AN=00006199-200307000-00004. Article Link
O'Brien, B. C., Harris, I. B., Beckman, T. J., Reed, D. A., & Cook, D. A. (2014). Standards for reporting qualitative research: a synthesis of recommendations. Academic medicine : journal of the Association of American Medical Colleges, 89(9), 1245–1251. https://doi.org/10.1097/ACM.0000000000000388
Users' Guides to the Medical Literature: Essentials of Evidence-Based Clinical Practice, Third Edition by Cochrane Interactive Learning consists of interactive modules that will teach you the basics of conducting a systematic review. You can download a certificate of completion for each module you work through. You will first need to create an account.
