How search engines work

Behind the scenes work for search engines starts with web crawling. Search engines "crawl" the web by visiting sites using an automated computer program sometimes referred to as a "spider". These spiders follow links from website to website learning information about what is available on the web sometimes storing all or part of the information contained in the HTML.

Next, the search engine will index the results of the web crawl. The content is analyzed and keywords that appear commonly on the page are indexed. Websites are ranked by relevance and popularity. A website that has more links pointing to it will rank higher in importance than other sites. There's a whole science behind developing a website that will rank highly called Search Engine Optimization.

Each search engine uses software to compile its own database of pages found on the web and has its own formula or algorithm for selection. This means each search engine will offer different results.

Lastly, here's where you come in: the search. On the next few pages you'll learn how to construct an effective search.