In this guide, we hope to demystify the terminology used around literature searching in the biomedical and health sciences. The terms and techniques discussed here will apply especially to databases used in the health sciences, but the basic principles apply to all database searching.

First, some basic concepts:

1. Many databases used in the health sciences, e.g.,MEDLINE, PubMed, CINAHL, and PsycINFO, utilize a thesaurus, also referred to as a controlled vocabulary. The thesaurus is a pre-defined list of vocabulary words known as "Subject Headings".
2. In databases that use a thesaurus, there are two primary ways to conduct a literature search: by Subject Headings using terms from the database's thesaurus, or by Keyword. We will discuss both techniques in this guide, although it should be understood that a Subject Heading search can only be conducted in a database that uses a thesaurus.
3. Relevant: When we are discussing the results of a literature search, we often refer to the "good" articles as being "relevant", and the articles that are off-topic as being "not relevant" or irrelevant". 
4. Sets: When conducting searches that involve the use of many different terms, it is especially helpful to run a separate search on each term, generating a separate set of results for each. Then, we will be able to combine these sets in various combinations to refine and focus our search. This is a much more sophisticated way of searching than simply combining all the terms together into one big search.
5. When we are talking about conducting literature searches, we are usually searching within the database records, not the full-text of the articles.
6. When we discuss a "search strategy", we are referring to the specific combination of terms and Boolean operators that we used to generate a set of search results.

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