the process of improving the visibility of a website or a web page in search engines

Search engine optimization (SEO) is the process of improving the visibility of a website or a web page in search engines' "natural," or un-paid ("organic" or "algorithmic"), search results. In general, the earlier (or higher ranked on the search results page), and more frequently a site appears in the search results list, the more visitors it will receive from the search engine's users.

Questions having the tag regards the implementation and use of SEO.

Reference: http://en.wikipedia.org/wiki/SEO