A search engine (sometimes called a Searchbot) is a tool (using both hardware and software) which indexes Web pages so that they can be retrieved by entering keywords into a search form.
Robots (a kind of software) called spiders go around the Web, indexing its content in vast databases so that they can be queried.
Since no search engine can reach all pages in one day (the whole process generally takes several weeks), each engine adopts its own strategy, with some going so far as to calculate how frequently certain sites are updated.
When the search engine's user fills out the form, he or she picks the words to be searched (and sometimes those not to be searched), with the help of Boolean operators like "and," "or," and "not" (symbolised by +, -, etc.). The request is sent to the search engine, which checks its databases for each of these words, then refines the search by removing the pages which don't fit the criteria.
It then returns a list of links to pages, adding the beginning of the pages' text, text specified by the page's creator using special tags called meta-tags, or even an extract of the page containing the words that were searched for.
These responses are ranked by relevance, as determined by the search engine's criteria, such as the percentage of words that match the search, their keyword density (the number of times the search terms are found in the page), etc.
A "metasearch engine" is a search tool which works by using the results of several other search engines.
Résultats pour Web Search engine
Résultats pour Web Search engine
Résultats pour Web Search engine
Résultats pour Web Search engine
Résultats pour Web Search engine
Résultats pour Web Search engine