A search engine is a software system that provides hyperlinks to web pages and other relevant information on the World Wide Web in response to a user's query.[1] The query is typically done within a web browser or a mobile app, and the search results are usually presented as a list of hyperlinks, often accompanied by textual summaries and images.
The word "engine" may seem like a misnomer, because a search engine is a standalone service provided to end users. However, for the search provider, the engine is part of a distributed computing system that can encompass many data centers throughout the world.
The speed and accuracy of an engine's response to a query is based on a complex system of information retrieval continuously performed by automated web crawlers. This can include data mining of a web server's files and databases, but Web content that cannot be accessed by a crawler is called the deep web.
There have been many search engines since the dawn of the Web in the 1990s, but Google Search became the dominant one in the 2000s and has remained so. It currently has a 91% global market share.[2][3] The business of search engine marketing has thus largely focused on Google.
A system for locating published information intended to overcome the ever-increasing difficulty of locating information in ever-growing centralized indices of scientific work was described in 1945 by Vannevar Bush, who wrote an article in The Atlantic Monthly titled "As We May Think"[4] in which he envisioned libraries of research with connected annotations not unlike modern hyperlinks.[5] Link analysis would eventually become a crucial component of search engines through algorithms such as Hyper Search and PageRank.[6][7]
The first internet search engines predate the debut of the Web in December 1990: WHOIS user search dates back to 1982,[8] and the Knowbot Information Service multi-network user search was first implemented in 1989.[9] The first well documented search engine that searched content files, namely FTP files, was Archie, which debuted on 10 September 1990.[10]