What is Search Engine? How Do Web Search Engines Works Actually?
A web search engine is software that searches keywords for anything on the World Wide Web and returns the results of WebPages that contains those keywords.
Every search engine use differences ways and each has different complex mathematical formulas to generate search results, but they all perform three basic tasks-
They discovered for content within the web pages or documents which is known as crawling
They reads these documents and creates an index based on the words contained in each document
They retrieve user query fetches a list of relevant pages.
Search engine scan everything on the web page like text, images, videos, keywords and linking etc. To find information on the hundreds of millions of Web pages that exist, a search engine use special software robots, called spiders, to build lists of the words found on Web sites. When a spider is building its lists, the process is called Web crawling. Then they collect the data from crawl and place it in their database and this process is called indexing. The purpose of indexing is to allow information to be found as quickly as possible. When you enter a keyword into the search engine, the search engine will look through the billions of web pages to help you find the ones that you are looking for.
Because a top search engine will index hundreds of millions of pages, many search engines not only just search the pages but also display the results depending upon their importance. This importance is commonly determined by using various ranking algorithms to build the ranking list that tries to present the most useful pages at the top of the list of search results.
There are many different types of search engines made by different companies, the most popular ones are Google, Yahoo and Bing.
Types of Search Engines:
1) Crawler-Based Search Engines:
Crawler-based search engines compile their listings automatically as explained above.
Crawler-based search engines are Google, Yahoo and Bing.
Directories uses human editor to compile their listings and they place websites within specific categories in the database. The human editors comprehensively check the website and rank it, based on the information they find, using a pre-defined set of rules. After a website makes it into a directory however, it is generally very difficult to change its search engine ranking.
There are two major directories Yahoo Directory and Open Directory
3) Hybrid Search Engines:
Hybrid search engines use a combination of both crawler-based results and directory results. More and more search engines these days are moving to a hybrid-based model.
Hybrid search engines are Yahoo and Google
4) Meta Search Engines:
Meta search sends the queries to other search engines and collect the results from them and them combine this result in one large listing.
Metacrawler, HotBot and Dogpile are Metasearch engine.