Spider is a component of the search engines that indexes the internet by “spinning” through the internet. A search engine spider (also called a Crawler or [ro] bot) follows links to various pages on your site and to others. This is why backlinks are so important (see SEO). The spider makes copies of the websites it visits and saves them in its search engine index, which is why only the pages that get spun come up when you search and it can differ from search engine to search engine and time to time.