A literature review (also called a research review or review of the literature) is a summary of existing research on a topic. It reviews the scholarly "literature" on that topic. It is often a preliminary part of a publication where the author identifies and comments on the relevant previous research, but it can also be a stand-alone work.
Guidance from the University of Southern California Libraries
Examples of published literature reviews:
Ferris, D., Hayduk, R., Richards, A., Schubert, E. S., & Acri, M. (2020). Noncitizen Voting Rights in the Global Era: a Literature Review and Analysis. Journal of International Migration and Integration / Revue de l’integration et de La Migration Internationale, 21(3), 949. https://doi.org/10.1007/s12134-019-00687-8