Web search engine is a tool design to search on the World Wide Web. It uses automated software a program knows as spiders or bots to survey the Web and build their databases. And without this tool, it would be virtually impossible to locate anything on the Web without knowing a specific URL. Some search engines also mine data available in news books, databases, or open directories. They store information about many web pages. There are lots of great search engines that deal primarily in academic and research oriented results.
Most search engines handle words and simple phrases only. In its simplest form, text search looks for pages with lots of occurrences of each of the words in a query. This design tool also makes some efforts to “understand” what is meant by the query words. But it cannot return hits on keywords that mean the same, and not actually entered in your query. Some search engines also allow you to specify what form you’d like your results to appear in, and whether you wish to restrict your search to certain fields on the internet. Most of the search engines return results with confidence or relevancy rankings. This is aware of such deceptive tactics, and has devised various methods to circumvent them, so be careful. It will not also give you access to all the information available on the Internet
There are 3 different types of web search engine. And they are all powered by robots .