How do search engines work?
The world wide web is a big place. If you know the web address, or URL, of a site you can find it by typing it into the address bar along the top of your browser. But what if you don’t know the URL?
You can find pages by following links from other pages but usually it is easier to search for things using a search engine.
These are programs that search an index of the world wide web for keywords and display the results in order.