All the parts of the search engine are important, but the search algorithm is the cog that makes
everything work. It might be more accurate to say that the search algorithm is the foundation
on which everything else is built. How a search engine works is based on the search algorithm,
which is closely related to the way that data is discovered by the user.
In very general terms, a search algorithm is a problem-solving procedure that takes a problem,
evaluates a number of possible answers, and then returns the solution to that problem. A search
algorithm for a search engine takes the problem (the word or phrase being searched for), sifts
through a database that contains cataloged keywords and the URLs with which those words are
associated, and then returns pages that contain the word or phrase that was searched for, either
in the body of the page or in a URL that points to the page.
But it even goes one better than that. The search algorithm returns those results based on the
perceived quality of the page, which is expressed in the quality score. How this neat little trick is
accomplished varies according to the algorithm that’s being used. There are several classifications
of search algorithms, and each search engine uses algorithms that are slightly different. That’s
why a search for one word or phrase will yield different results from different search engines.
Search algorithms are generally divided into three broad categories: on-page algorithms,
whole-site algorithms, and off-site algorithms. Each type of algorithm looks at different elements
of a web page, yet all three types are generally part of a much larger algorithm.