Where does all indexed elements get saved?

Once we define indexing rules for wsdl artifacts, and indexing gets completed, where these indexed elements get saved?

Is it in Index_folder?? if yes/no can anyone give the exact location where it will be saved? And what format does it gets saved?

Also which search index engine RAM uses? Is it some open source search engine/ or RAM specific search engine? As if provided the search ingine name, if open source the indexed file can be read and used.