There are two checkboxes on the basic search page. The first allows you to limit your search to the domain of the machine you are currently logged into. The second causes a thesaurus lookup of your search phrase. Search results will include resources which match any of the related phrases as well as the original phrase.
The resource metadata fields searched in a basic search are listed below. It is worth noting that the data searched are self-reported by the resource author. In many cases, authors are unable to provide relevant values for the fields searched. If you need to search based on properties other than the following, use the Advanced Search link on the basic search page.