Nowadays if you need to find information on any topic, you just type what you’re looking for in a search engine and get a staggering list of web pages to read.
But how it actually happens that you get relevant results for your search? What do search engines do to return to you the information you want?
There are differences in the ways various search engines work, but they all perform four basic operations to provide search results:
Searching the Internet
Search engines are crawling the World Wide Web for data using software agents called web crawlers, also known as robots or spiders. Those are automated programs which constantly browse web pages in a methodical manner following every link found within the site. The crawler will periodically come back to the sites to check for any information that has changed.
Indexing web pages
After a web site has been crawled, its content is indexed which means stored in a database of information that build up a search engine's "index". Search Engine indices are lists of the words found on web sites, their URLs, the number of times that the word appears on a page, etc.
Processing inquiries for information
When you ask a search engine to locate information, you are actually searching through the index that the search engine has created and not the web. Your request for information comes into the search engine and it quickly retrieves from its depository all the data that match your query.
Ranking results
Once the search engine has determined which of the results match your inquiry, the engine's algorithm analyzes each of them to decide which is most relevant to the submitted request. The search engine’s ranking system lists the results from most relevant to least. The same search on various search engines may produce different results as they don’t use the same algorithm to search through their indices.