A review of the literature is often necessary in order to survey and analyze current (you determine time frame) literature relating to a particular issue, problem, theory, methodology, model, framework, etc.
A thorough literature review involves a comprehensive search of all known/findable scholarly literature that addresses the topic. In some cases other types of sources, such as books or book chapters, theses or dissertations, “gray literature” such as technical reports, documents, media, social media, or conversations may also be appropriate.
The written review provides a summary and analysis of this literature in order to put research into a context, to explain what has been done to date, and/or to identify gaps or missing elements.