DSpace’s discovery module  enhances the overall platform search capabilities, and was first integrated with the XMLUI in version 1.7.0 . The discovery module, once activated, enables faceted searching and browsing. Faceted search/navigation/browsing is widely used in a number of sites. Some notable use of faceted searching include Google’s search engine  and LinkedIn’s faceted people search feature [4, 5].
The discovery module is not active by default, however, this tutorial  on the DSpace wiki site comprehensively provides details on how to enable discovery module. An important thing to note is that the Discovery module is currently only compatible with the XMLUI.
The screencast below illustrates how to go about enabling the the Discovery module on DSpace 1.8.2.