Search engines are information retrieval systems with the primary purpose of helping find information, whether that be on a single computer or a network of computers. The term search engine, though general, usually refers to web search engines, which have become the primary portal used by internet users to locate information they need on the web.
Web search engines work by sending out search engine robots, often referred to as bots, crawlers and spiders, to index the content web pages.
The contents of each page are analyzed to determine what topics they fall under. This is done to make information retrieval of the pages found in the search engine’s pages much faster.
Once the pages are indexed they are also rated or ranked for each for keywords and phrases in comparison with other pages that have the same content. This is done to give search users the best possible results for the search terms they are looking for with relevance, popularity (reputability) and quality of content being the top factors considered.
Ranking well on search engine results pages have become so important in getting more people to visit a site that an entire industry has been built upon the whole concept. Search engine marketing is a type of internet marketing that focuses on getting more traffic to a site with the end goal of creating more revenue from the website, whether that be due to ad clicks, online purchases, etc. It relies heavily on search engine optimization to rank well in SERPs.