The controlled vocabulary used by the MEDLINE database is called Medical Subject Headings, or MeSH. You can access the MEDLINE database in PubMed or in EBSCO; although the two platforms both house the MEDLINE collection, the way they behave are different.
Let's look at an example: First, go to the MeSH database, and search for "Phthises."
MeSH indexers who have read the current biomedical literature agree that the topic of Phthises is best described as "Tuberculosis, Pulmonary." A search in MeSH for any of the synonyms for this topic take the searcher directly to the "Tuberculosis, Pulmonary" Subject Heading. From there, searchers can see the term's definition and all the synonyms for this topic (listed as "Entry Terms"), the related Subheadings, and the place(s) in which the topic appears in the MeSH hierarchy.
The video below explains how to use MeSH in Pubmed. Additional information on using MeSH in EBSCO is linked below.
When using MeSH terms, Pubmed automatically "explodes" the subject heading -- this means that Pubmed will search for your subject heading, but it will also search for any subject headings underneath that term in the MeSH tree. This will expand your search results. For example, if you were searching for Tinea, you'll also see information about Onychomycosis, Tinea Capitis, etc.
If you want to turn off Pubmed's automatic explode option, you can add the following to your search [mh:noexp]
MEDLINE in EBSCOhost, on the other hand, does not automatically explode terms. When browsing the MeSH database, you'll see an optional checkbox to "explode" the search term. This means that the database will search for your subject heading, but it will also search for any sub-headings underneath that term. This will expand your search results. In general, it is recommended to explode your search.
The "major concept" checkbox in EBSCO will limit your results just to articles where the subject heading has been designated as a major concept. This will reduce your results, and unless you are working with a huge amount of search results, we recommend that you do NOT check the "major concept" box.
PubMed / MeSH Interactive Tutorial