Search engines are the software that helps find information online, a task they perform by using complex algorithms. These algorithms identify pages on the web that match a particular search query and then present them in a list. These results can be a mix of webpages, articles, photos, videos and other types of files. Some search engines also mine data available in public directories and databases.
As the internet became increasingly populated with commercial and research reference information, it was important to create ways for people to quickly and easily access this material. Eventually, a new type of machine was invented that could crawl the world wide web and find information relevant to specific queries. This machine is known as a search engine and it has become one of the most important tools on the web.
A search engine is a piece of software that searches the internet for information, based on textual searches that are entered into a search box. It then combines this information in an ordered list of results that are presented to the user. Generally, the most relevant results are shown first. A search engine is able to achieve its goals by using complex algorithms designed by teams of computer scientists.
Most search engines work in three main stages: crawling, indexing and ranking. To crawl the world wide web, a programmed searchbot (also referred to as a spider, ant or robot) is sent out to gather information about websites and their pages. These pages are then stored in a database, sometimes referred to as an index. The index can then be accessed by a user through a web browser to provide results for the query that was entered into the search engine.
The most challenging stage for a search engine is judging the relevance of each result in its returned list. Because the Web is a large, unorganized collection of information, any given query may produce hundreds, thousands or millions of “hits” in its return list. The challenge is to determine which of these hits are most useful and reliable, which can be done by analyzing the content of the page, identifying authoritative sources that many pages refer to and assessing the quality of the information.
The most advanced search engines use sophisticated algorithms that take into account a myriad of factors in order to give the best possible results to users. Some of these factors include relevancy, accessibility, usability, search popularity and other social signals. There is even a whole science dedicated to making sure a website ranks high for its category, and this discipline is often called search engine optimization, or SEO. This cat-and-mouse game between search engines and sites has led to a variety of tricks that can be used to improve a site‘s ranking. These techniques can range from ensuring keywords are repeated in natural context to intentionally placing certain words and phrases on the page to attract the attention of a search engine algorithm.