PubMed offers its Medical Subject Headings (abbreviated as MeSH) as its form of subject terms.
PubMed offers automatic subject term mapping. That is, if PubMed can match your keyword to a subject term it will do that automatically. For example, if you search on cancer, PubMed will translate that automatically in the MeSH term Neoplasm. Note, that you can only see this by going into the Advanced search tab on your search results and clicking the dropdown arrow under "Details". If you do that for your cancer search you will see the following details about how PubMed is translating your search:
This automatic translation makes it easy to build searches, but sometimes--especially for things like systematic reviews--you will want to build a MeSH search from scratch. See below for how to do this.
To begin a MeSH search, go to the PubMed homepage and find and click the link for MeSH Database in the lower right of your screen.
This will bring up a search screen. Note that this is for searching for MeSH terms and not for searching for article information--that will come later.
You can select one of the suggestions made by PubMed, or--as we want in this case--click "Search". That will bring up a list of MeSH subject terms for you to select from. In the following example we will select Neoplasms.
When you click Neoplasms you will get a detailed page for the MeSH entry on Neoplasms. See below for a more detailed explanation of this page.