Search engine spidering ?
First of all, search engines use a technique known as spidering in order to collect information from web pages. This involves downloading web pages, and following links on them to other pages and in turn downloading those pages. By this process, a search engine spider can locate and store billions of web pages, building up a large database of as many pages as possible. Many search engines refer to their stored web pages as a ‘cache’, and you can often see links to ‘cached’ pages on search result pages.
