Subject headings are a "controlled vocabulary," an organized list of terms assigned to database resources that assist in organizing all resources.
The most common subject headings are created and maintained by the Library of Congress, which are sometimes referred to as the Library of Congress Subject Headings (LCSH). Most databases use LCSH to organize resources, which is why they can act as possible keywords or phrases.
If you are searching for medical and health sciences literature, those resources are organized using Medical Subject Headings or MeSH terms. MeSH terms work similarly to the Library of Congress Subject Headings.
To search by subject headings:
This video explains how to use classification codes in APA PsycInfo on the EBSCO platform to refine your research. Classification codes group articles, book chapters, and dissertations by broad subject categories. They're useful when you have too many search results or want to focus on a specific subfield.
This video provides a guide on how to use the methodology limiter in APA PsycInfo to find journal articles that use a specific study design. Although the video provides a demonstration in a different database, EBSCO also provides the same type of methodology limiter.