Briefly, when you enter your search into the box, PubMed will analyze your terms and add related terms to your search. These related terms will include synonyms and the appropriate Medical Subject Headings (MeSH) terms.
To learn more about searching in New PubMed, click the image to the right for brief video tutorials on how to Pubmed uses automatic term mapping and MeSH terms to find citations for you!
There are a number of tricks you can use to enhance your PubMed searches.
Knowing how to use these techniques - on their own and together - will help you narrow your search when you have too many irrelevant results as well as broaden your search when your search when it's too limited.
Here are a few more tutorial videos on different types of searches:
The links below are resources for the legacy version of PubMed.