A literature review is a comprehensive summary of the ideas, issues, approaches, and research findings that have been published on a particular subject area or topic. However, it is not a simple description of all that the reviewer has read on the topic. It is better understood as a critical synthesis (or bringing together) of :
The review should be organized with a clear purpose and scope defined by the author of the review and should not be just a summary of existing research on the topic.
Literature reviews in social work increasingly focus on evidence-based research found in scholarly journals but there is some discussion within the profession that focusing only on evidence-based studies minimizes the importance of other sources of knowledge, including that gained through practical experience. Material published by think tanks, professional associations, and research institutes may provide valuable current information about a particular topic but they are often not peer-reviewed or evaluated for reliability and validity as is the case with research articles found in scholarly journals.
 Kiteley, Robin and Chris Stogdon. Literature Reviews in Social Work. Sage, 2014