First, there are the primary studies that researchers conduct and publish.
Second are the reviews of those studies that summarize and offer new interpretations built from and often extending beyond the primary studies.
However, note that they can also introduce problems of bias when they are used to make summary claims of the sort found in systematic reviews [see below].
Integrative Review Considered a form of research that reviews, critiques, and synthesizes representative literature on a topic in an integrated way such that new frameworks and perspectives on the topic are generated.
Typically it focuses on a very specific empirical question, often posed in a cause-and-effect form, such as "To what extent does A contribute to B?
" This type of literature review is primarily applied to examining prior research studies in clinical medicine and allied health fields, but it is increasingly being used in the social sciences.
A literature review surveys books, scholarly articles, and any other sources relevant to a particular issue, area of research, or theory, and by so doing, provides a description, summary, and critical evaluation of these works in relation to the research problem being investigated.