Reference is a category for sites devoted to the study of and access to information itself - teaching it (Education), using it (Knowledge Management), storing it (Libraries, Museums) - or sites containing information on topics varied and comprehensive enough that they could not be classified under the other top level Open Directory categories (Dictionaries, Directories, Encyclopedias).
Thanks to DMOZ, which built a great web directory for nearly two decades and freely shared it with the web. About us