There is much confusion about what a literature review is. Many people use "systematic review" and "literature review" interchangeably and that is where the trouble starts.
Difference between a systematic review and a literature review
Some clear definitions:
Literature review - provides an examination of recent or current literature. A literature review may cover a wide range of subject matter at various levels of completeness and comprehensiveness based on analyses of literature that may include research findings. Lit reviews provide the researcher/author and the audiences with a general image of the existing knowledge on the topic under question. A good literature review can ensure that a proper research question has been asked and a proper theoretical framework and/or research methodology have been chosen. To be precise, a literature review serves to situate the current study within the body of the relevant literature and to provide context for the reader.
Scoping review - Exploratory in nature, scoping reviews (sometimes called mapping reviews) present the literature on a topic; identify key concepts, theories, and sources of evidence; and can be used to create working definitions, analyze concepts, or better understand a phenomenon. A scoping review is less likely to address very specific research questions or to assess the quality of included studies. Scoping reviews are often conducted before a systematic review when the achievability of research is in question, because either the relevant literature is vast and diverse and/or little literature exists.
Systematic review - the overview of several randomized trials of the same intervention or treatment for the same situation or condition; this overview systematically and critically reviews and combines all the studies, providing a better answer than the results from just one study. Systematic reviews are described as the most reliable source of evidence to guide clinical practice. The purpose of a systematic review is to deliver a meticulous summary of all the available primary research in response to a research question. A systematic review uses all the existing research and is sometime called ‘secondary research’ (research on research). They are often required by research funders to establish the state of existing knowledge and are frequently used in guideline development.
Systematic review with meta-analysis - A systematic review attempts to gather all available empirical research by using clearly defined, systematic methods to obtain answers to a specific question. A meta-analysis is the statistical process of analyzing and combining results from several similar studies.