A search engine is a software system that searches the World Wide Web in a systematic way for information specified in textual queries, and presents results in a line of web pages, commonly known as a search engine results page (SERP). A variety of techniques exist to improve the performance of websites on a search engine, such as using structured data, improving metadata, making proper use of alt tags on images, and optimizing the site‘s content. Several types of search engines are available, including web, database, enterprise and mixed-platform.
Modern search engines are sophisticated, highly intricate software systems that process trillions of web pages to provide relatively well-aimed resources for a user’s query. They require large numbers of computers to operate, and utilize massive amounts of data storage.
Most search engines work by scanning the Internet for pages that contain specific keywords. The information on the pages is then compared to the keywords in a user’s query, and the most relevant pages are returned as the top results. Some search engines also mine data available in databases or open sources, and provide results that include links to other types of media such as videos, images or infographics.
Various algorithms are used to determine the relevance of a particular page or site for a given search query, and the most popular and successful engines tend to be those that use these algorithms with the highest degree of accuracy. The algorithm may scan the words on a page, or look at other elements such as the frequency with which those words appear, and the context in which they are found. It may also scan and compare the popularity of other sites that link to a page, and look at the pages that these links come from.
Another element that is often analyzed is the way that pages are linked together on the Web, and the way in which other pages or sites reference or quote these references. It is not uncommon for a single word to appear on many different pages, and this can influence the search engine’s determination of its relevance. Search engine technology is becoming increasingly sophisticated to discourage what is known as keyword stuffing, where a Web page contains a word or phrase too many times in order to artificially increase its ranking.
Other tools and methods that are used by some search engines to improve the relevance of their results include adding keyword phrases to the title or abstract of a page, as these are often listed separately from the main body of text, and the inclusion of keywords in the alternative description (alt text) of images, as this is used by assistive technologies to make Web pages more accessible for users with visual impairments. The addition of metadata such as reviews, ratings or other descriptive information can also help a page to rank more highly for specific searches.