The purpose of a systematic review is to find, select, and summarize all available evidence on a specific research question using a predetermined and reproducible method.

A systematic review is characterized by the following requirements:

• A predefined search protocol specifying the purpose, key concepts, and methods, inclusion and exclusion criteria for the systematic review
• Research questions can be formulated based on the PICO framework (Population, Intervention, Comparison, Outcome)
• Accurate documentation of each step and decision along the way - so that the reader can follow and evaluate the reviewer's method
• The literature search should, in principle, identify everything written about the topic (including grey literature) to avoid bias
• Use of established standards for assessing the quality of included studies (critical appraisal) and reporting the results (e.g., PRISMA)
• It requires two people or a team to conduct a systematic review, especially in terms of screening articles and extracting data

Read more about systematic reviews in the Campbell collaboration, in the manual from the Joanna Briggs Institute, and in the Cochrane handbook, where you can also learn about literature searching for a systematic review.

Scoping reviews are often referred to as precursors to systematic reviews, as they involve mapping out existing literature within a field.

In scoping reviews you can investigate, among other things, the quantity of literature available, how topics are addressed, and identify gaps or areas in need of updates within a field. In other words, scoping reviews help to provide context for a given research area. Often, you cover a slightly broader range of topics, including various types of studies, compared to a systematic review. Research questions can be formulated using a PCC (Population, Concept, Context) framework.

There is a reporting standard for scoping reviews available from PRISMA, but there is no formal quality assessment.

Learn more about scoping reviews in the manual from the Joanna Briggs Institute.

Research literature review is an overarching term for reviews that utilize the systematic and transparent approach of systematic reviews.

In a research literature review you conduct a thorough exploration of the scientific literature within a specific field in a structured and systematic manner. However, you may not necessarily use established standards for search protocols and reporting. The purpose is often to map out what has been written about an issue and may resemble what is known as a scoping review.

A narrative review does not follow a specific systematic method but relies on the author's interpretation and perspective.

In the traditional narrative review the basis for the literature review is often a defined amount of literature selected by specialists in the field and reviewed according to specific relevance criteria.

The process of the information search and selection is not necessarily described systematically or explicitly but is based on a critical selection and evaluation of key literature.

The goal is often to present "the current state of knowledge" about a specific topic or field. There is often also a desire to present new perspectives, conceptualizations, or understandings through the review.

The research question is driven by analytical interests. The focus is on creating meaning and understanding, as well as providing a thorough overview of key issues, theories, studies, and methods within a research area. It is often communicated narratively and can be an analytical synthesis of the current research literature. The aim may be to conceptualize the current research agenda, theory development and perspective on future research.

There is no gold standard for how a traditional narrative review is reported. However, it is implicitly understood that it should follow traditional academic guidelines.

In short, a rapid review is a simpler and faster form of systematic review.

In a rapid review you have a focused question developed using the same method as a in systematic review. However, you have limited time and resources (budget).

Therefore, the literature search is focused and delimited, and there is a pragmatic approach - for example by limiting to specific years, languages, and countries - and by using fewer databases.

Since rapid reviews can have greater bias transparency and thorough documentation are especially important.

Read more in the guidance on rapid reviews published by Cochrane.

An umbrella review is also known as "review of reviews" or "overview".

You can conduct an umbrella review when there is already a multitude of high-quality systematic reviews on the same topic.

In the literature search you look for reviews rather than primary studies. In some umbrella reviews you assess the quality of the primary studies included in the found reviews.

The purpose of umbrella reviews is to summarize existing knowledge with recommendations for practice. They also highlight areas where knowledge is lacking and suggest potential future research directions.

Read more about umbrella reviews in the manual from the Joanna Briggs Institute.