user authentification with apache

This might not exactly be the right place to ask this, but could someone help me with this. I would like to have a user authentification on my site, so that only users who are logged in can view certaing pages. I've understood that apache has some functions for this, but how can I enabled and use them? I didn't find much about this on the apache.org site :/ Maybe someone here has some good links and/or info concerning the subject? - tk