SEO or Search Engine Optimization is the name given to an acitvity that attempts to improve search engine rankings. In Search results Google displays links to pages it considers relevant.

Search engine optimization is the regular practice of optimizing a web site by improving internal and external features in order to increase traffic from search engines. Optimizing a web site for search engines requires understanding and evaluating many unique elements of the website. SEO is all about making a website search engine friendly to generate much needed traffic to the website.

Search Engine Optimisation or SEO is the simple activity of ensuring a website can be found in search engines for words and phrases relevant to what the site is offering. In many respects it's simply quality control for websites.