SEO stands for Search Engine Optomisation.
It is the process of changing the code and content of a page to make it more search engine friendly. By making changes to a web page that take SEO into consideration, that web page can be made to be displayed higher up a list of search results in a search engine like Google, Yahoo or Bing. Wikipedia has a much more complete explanation
. The second and third paragraphs are particularly pertinent.
Many things affect how high up search pages a web page comes, this Instructable looks only at the factors that YOU the author can change or influence. A lot of behind the scenes magic is already done by Instructables to cater to the search engine crawlers and the fact that Instructables links to and is linked to by so many other sites also helps make it a good place to publish work to get it seen instead of a small personal website or blog.