Search engines are means certain strategies , the use of specific computer programs to collect information from the Internet , the information is organized and processed to provide users with search services , users retrieve relevant information presented to the user system . Search engines , including full-text index , directory index , meta search engines, vertical search engines , a collection of Search engine search engine and portal free link lists. Baidu and Google and other search engines behalf .

Full-text search engine is widely used in the major search engines , foreign representatives Google, the country is famous degree Baidu , Soso . They extract information from various internet websites ( web- text-based ) , data can be retrieved and set up user records that match the query criteria , according to the order to return certain results .

Depending on the source of the search results , full-text search engine can be divided into two categories, one with its own search program (Indexer), commonly known as " spiders " (Spider) program or "robot " (Robot) program that can self-built web database , search result of the call directly from their own database, mentioned above belong to such as Google and Baidu , Baidu exists auction ads ; other is rented other search engine's database , and then arranged in a custom format search results, such as Lycos search engine.

Classified section in the search engines mentioned full-text search engine to extract information from a website to build web database concepts. Search engines are two automated information search function . One is a regular search , that every so often ( such as Google usually 28 days ) , the search engine initiative to send a "spider " program on Internet sites within a certain range of IP addresses to retrieve, once found a new site , it will automatically extract website information and URL added to their database. Another is to submit your site to search that site owners to voluntarily submit URL to search engines, it is within a certain time ( ranging from two days to a few months ) directed to your site to send a "spider " program to scan your site and relevant information stored in the database to prepare the user's query . With search engines indexing rules change dramatically , the initiative does not guarantee that your submission Web site can enter the search engine database , the best way is to get some external links and more , so that the search engines have more opportunities to find you and you will automatically site included .

When a user with keywords to find the information, the search engine will search in the database, and if found consistent with the content of the website user requirements , it uses a special algorithm, usually based on the degree of matching keyword pages , occurrence , frequency, link quality calculate the relevance and ranking of each web page rank , then according to the level of correlation , in order to link these pages back to the user . This search engine is characterized by full rate is relatively high.