Each listing can optionally have a "Qualifier" appended to it, so that in addition to your visitor being able to view the raw results of a search or a category, they may optionally "refine" their search results by some common thread. Typically, a set of qualifiers would be states, countries, etc ... something common enough to make sense for every category/link in the system to have associated with it.
When you have the qualifiers option turned on in the admin center, the search plugins (<!-- PLUGIN:SEARCH -->, etc) will automatically show a drop down list containing your defined qualifiers. If the search selects a qualifier and presses the search button again, their search will be pared down, showing the raw search matches that also meet the qualifier criteria.
