The literature review is a comprehensive overview of research studies and theoretical arguments regarding some phenomenon or phenomena. For communication researchers, a complete literature review is a carefully considered argument that posits a particular state of the world. This proposed state of the world is based on the evidence provided within the sources included in the review. Literature reviews should be used to identify not only what research and theorizing has already been conducted on a particular subject but also what research has yet to be done. In other words, literature reviews highlight both what the scholarly community knows about a subject and what it has yet to learn. This entry introduces different types of literature reviews and their accompanying goals.