MeSH (Medical Subject Headings), the National Library of Medicine's controlled vocabulary thesaurus, consists of terms naming descriptors in a hierarchical structure that permits searching at various levels of specificity.
In other words, MeSH terms describe what a review is about and are used to label all reviews on a topic even if different authors use different words for the same concept (such as cancer vs. neoplasm vs. tumor).
Note: you can also search for MeSH terms from the Search Manager (also accesible from the search box).