The “Broaden Search” button appears in BiblioCommons after performing a search. In the Classic Catalog the “Show Similar” button appears on the detail page only after you’ve performed a keyword search. When you click on either button, another keyword search is performed to find subjects close to your original search.
For example, if you did a keyword search in the Classic Catalog on Columbus, and on the results page, you clicked the “Where is it?” link for the first item, a book called Christopher Columbus: To the New World, you would get a detail page that has a “Show Similar” button at the top. If you click on that button, it will do a search for subjects related to Columbus. The results list will show books about other explorers, such as Captain John Smith or Hernando de Soto. If you click on the “Where is it?” link for one of those items and scroll down, you’ll see the subjects that the “Show Similar” button searched for highlighted in red.