To summarize, when you search PubMed with a phrase, PubMed’s Automatic Term Mapping (ATM) attempts to map it to a MeSH term and breaks the phrase apart and processes each term individually.

This diagram illustrates these steps:

For most searches, PubMed’s ATM will return results related to your phrase. There may be times, however, that you get zero results or irrelevant results for a phrase. The next module of this tutorial will demonstrate search strategies you can use if that happens.