True search engines
§“True” search engines are created by machines.  Databases are built by “robots” or  computer programs that roam the WWW finding sites new to their home database, updating old ones and deleting obsolete sites.
§
§A spider visits a web page, reads it, and then follows links to other pages within the site (this process is called being "spidered" or "crawled”)
§
§The spider returns to the site on a regular basis to look for changes and this may affect how sites are listed and retrieved.
n
Hotbot http://www.hotbot.com/ is an example of a true search engine.  Parts of a search engine include the "spider" and the software.  A search engine works by sending out "spiders" to record information about each site. If you change your web pages, search engines eventually find these changes, and that can affect how you are listed. Page titles, body copy and other elements all play a role.  When doing a search, the software looks for matches based on the elements of the sites that it has stored in its index.