This document defines and discusses literature reviews. It begins by stating that a literature review summarizes previous research on a particular topic, identifying and synthesizing relevant studies. It then discusses the purpose of literature reviews, which is to provide background knowledge, avoid duplication, identify gaps or inconsistencies in prior work, and position new research in the existing context. The document outlines three main types of literature reviews - simple, applied, and academic - and notes the distinguishing characteristics of an academic literature review. It includes a figure illustrating common elements and provides a table contrasting the advantages and disadvantages of conducting literature reviews.