The key to a search engine’s success is its ability to efficiently and rapidly classify and categorize all content. Being able to do this gives the engine an almost sentient understanding of what a properly written article should look like and it is all done with the assistance of searchers. Everything in the search engine algorithm boils down to what a customer thinks of a site. And they do not need to ask them in a poll, they just need to watch how the average searcher behaves.
Every time a person enters the search engine, a cookie is planted in their browser and from there every person is recorded for what the search. A pattern develops form here and most people go in and search for the same things. From this information engines are able to determine how the global aggregate searches for any particular keyword, they are also able to determine how a particular community searches for a keyword. This is important as it allows the engine to return results catered to that area.
For instance, a person in New York searching for dental service will only be returned results of dentists in the New York area. The search engine has learned over time that hose in New York are not going to search for dentists in Boston. In the same way, if they sought information about Wal Mart, it would return results of the Wal Mart locations in New York.
The engines do not know that Boston is not convenient for a New Yorker when searching for a dentist butt he learn that when a person searches for a dentist they want something in the vicinity. That logic applies to New Yorkers as well as Londoners and every other city in the world. That’s the level of what the search engine learns every time an action is executed. It learns the behaviour of the person. Once it understands the person, it categorizes that person’s searches and habits.
To attest this, think about it using the search engine to find something then a few days later notice how the advertisements that appear on the website you visit seem to be selling that product or something close to it. It’s because that cookie that is planted in your browser now is linked to the profile in the search engine. Advertisers have bought advertisements from the engine with instructions to target a person who has searched for a particular product in the past.