How Search Works

This is definitely not new, but Tim Bray's excellent series of articles on Search is still relevant today and deserves recognition:

http://www.tbray.org/ongoing/When/200x/2003/07/30/OnSearchTOC

If fifteen articles is too much, at least take the effort to read on the underlying principles:

http://www.tbray.org/ongoing/When/200x/2003/06/18/HowSearchWorks