The Advanced link provides two options to refine a search:
MeSH (Medical Subject Headings) is the U.S. National Library of Medicine's controlled vocabulary.
Access MeSH in PubMed from the drop-down menu OR click on MeSH Database from the PubMed homepage.
Enter a topic into the Search bar and click the Search button. The MeSH database offers options to clarify and focus searches.
Click the selected MeSH term to view the definition, often with the year introduced, the entry terms with the subheadings, related and linked terms, also MeSH hierarchy of linked terms.