The search engine functions in the same way your library card functions to catalog books inside that labyrinthine store room of information. The only difference is that library cards are manually indexed by human minds. Search engines, on the other hand, are mostly administered by web robots or crawlers who sift through the word content of each and every webpage published on line.
A search engine crawler is also sometimes referred to as a web crawler. This is a program which is used to scour the entirety of the World Wide Web or the Internet. It also has rather apt bug-like names including ants, web spiders, web skutters, web robots, bots, and automatic indexers. When people refer to the process of indexing web pages, though, they call it “spidering” or “web crawling”. Search engines run on these spidering or web crawling methods to update their indexes.