To carry out even the most basic search, it is useful to have an understanding of essential search techniques:
Experienced searchers might use a variety of more advanced techniques.
Also see our guides to searching individual databases:
Subject headings are similar to tags or hashtags. They describe the topic of an item in a database.
However, unlike tags they come from an official, standardized set of terms and are assigned by experts.
The index of subject headings is usually called the Thesaurus.
Many resources have their own list of subject headings, or thesaurus. For example, the database Medline has a thesaurus called MeSH (Medical Subject Headings).