Whenever you carry out a search on Google, Yahoo, Bing or other major search engines you see two results - the advertising (Paid Search Results) and the actual suggested pages (Organic Search Results).
The adverts are not there by chance, it is because the advertiser is paying to appear whenever an internet user searches a particular word or phrase. How well the advertiser organises their PPC (Pay Per Click) advertisement and how much they are prepared to pay affect where their advertisement appears in the list of adverts - in other words how well it ranks in the Paid Search Results.
There is great skill to this and it is possible to pay less per click than your competitor but still appear above their advertisement.
Paid Search Results and their management are a complete branch of SEO (sometimes called SEM - Search Engine Marketing) because it can take skill and experience to rank at the top of the Paid Search Results while paying less than other advertisers
Next there are the 'real' search results - those web pages the search engine thinks are relevant to the words you are searching. No one has paid for them to be there.
These results are known as Organic Search Results and SEO is all about helping individuals or businesses rank better here - after all once you are then visitors are free!
I'm Tim Hill, a Search Engine Optimisation and Online Marketing specialist. I created this site to help others understand that SEO is not a mysterious black art!.
If your a newbie try the Getting Started in SEO page, otherwise feel free to dig around and learn more.