Open the database and click on subjects below the main search bar. 

 
This is a thesaurus of educational terms that will help you build a better search.  It is great at helping you brainstorm synonyms to try, think of narrower topics, and see broader themes in your topic.
Put a term in the search box and choose a term in the results.
The resulting page will often give you a definition of the term, include broader, related, and/or narrower terms, and show you terms that may no longer be in use but be synonyms.

 
Click a linked term to "explode" it and see terms related to it, or write some down to try in your search!