Knowledge synthesis is a term used to describe the method of synthesizing results from individual studies and interpreting these results within the larger body of knowledge on the topic. It requires highly structured, transparent and reproducible methods using quantitative and/or qualitative evidence. Systematic reviews, meta-analyses, scoping reviews, rapid reviews, narrative syntheses, practice guidelines, among others, are all forms of knowledge syntheses. For more information on types of reviews, visit the "Types of Reviews" tab on the left.
A systematic review varies from an ordinary literature review in that it uses a comprehensive, methodical, transparent and reproducible search strategy to ensure conclusions are as unbiased and closer to the truth as possible. The Cochrane Handbook for Systematic Reviews of Interventions defines a systematic review as:
"A systematic review attempts to identify, appraise and synthesize all the empirical evidence that meets pre-specified eligibility criteria to answer a given research question. Researchers conducting systematic reviews use explicit methods aimed at minimizing bias, in order to produce more reliable findings that can be used to inform decision making [...] This involves: the a priori specification of a research question; clarity on the scope of the review and which studies are eligible for inclusion; making every effort to find all relevant research and to ensure that issues of bias in included studies are accounted for; and analysing the included studies in order to draw conclusions based on all the identified research in an impartial and objective way." (Chapter 1: Starting a review)
What are systematic reviews? from Cochrane on Youtube.