How Google works , How a normal Search engine works
Found a good image explaining the intricasies of a search engine, the image states Googles working but any search engine will use
almost all of the steps described described in the image but yes googles excels at it :)
if you cant see the image above visit the site
http://xs.to/xs.php?h=xs21&d=05123&f=what_happens_when_u_google.jpg
or
http://images5.theimagehosting.com/what_happens_when_u_google.jpg