A literature review is a thorough and up-to-date overview of existing research about the topic being studied. The literature may come from books, articles, documentaries, interviews, critical reviews, DVDs, or other formats.
It's a review because it usually contains a summary, synthesis, or analysis of the central arguments in the existing literature on the topic. A literature review does not present an original argument, but instead presents the arguments of others. The sources are the main focus in a literature review and the author summarizes the arguments or ideas of others. You should include only the most relevant sources on a topic.
The literature review may also include gaps in the literature, identifying areas where further research needs to be completed.
The literature review is organized in a way that shows the relationship between research studies, as well as the way each has contributed to an understanding of the topic.
Since it is an overview of existing research on a topic, the literature review is a secondary, rather than primary, source.
A literature review can have several purposes.
A researcher cannot perform significant research without first understanding the literature in the field.