The algorithm for search engines is basically a formula that tells Google where to position each site based on a number of SEO related factors. It looks at the topics that are being talked about on each page and each linking website and makes an educated decision about the quality of each website.
This formula is how SEO’s are able to move websites within the Google search engine. The ranking structure is merely an equation and it isn’t perfect by any means. It often ranks some non-deserving websites way too high and some great websites are on the bottom of the pile.
A good seo can come in and look at the algorithmic nature of the words and phrases surround a particular website and change them in a way that will appear to the search engine as something worth ranking.
You must remember that a search algorithm is nothing more than a formula and formulas can be solved. When you start to do SEO you’ll begin to notice patterns that will suggest the way the algorithm works. This is the only way of doing it because there is no clear answers given by Google or schools on how exactly any of this works. On top of that, the way sites are ranked is constantly being updated and changing through the years. All you can do is try to keep up and hope that things fall in your favor.