PubMed uses a specific set of subject terms, called MeSH (medical subject headings), to tag articles pertaining to specific subjects. MeSH can be used to help pull relevant articles pertaining to a certain topic, even if the articles use different keywords.
Search for relevant subject headings using the MeSH Browser.
Clicking on a subject heading will bring up the heading details, including which keywords map to the heading (these are called entry terms), when the subject heading started being used, and available subheadings. It will also show the MeSH term's place in the MeSH hierarchy, which can help discover more broad or narrow terms.
NOTE: If a MeSH term has been introduced in recent years, that term is a day-forward change and will not be applied to articles published before that date. In some occasions, the year introduced will be followed by a date in parentheses. In these cases, the term has been applied retroactively to literature published from the present back to the year in parentheses.