The literature review is an overview of significant literature on a particular topic. It puts your own particular question in the context of current and previous research. The purpose of a literature review is to establish what is currently known about a specific topic and to evaluate the strength of the evidence upon which that knowledge is based.
In evidence-based medicine, clinical decision-making is based on a combination of individual expertise, patient values and the integration of the best available evidence from systematic research. A systematic review includes a comprehensive search for primary studies on a particular clinical question, the critical evaluation of these studies and a synthesis of results according to a pre-determined methodology which may include meta-analyses of data.