SEO stands for "Search Engine Optimization". As search engines such as Google, Yahoo and Ask experienced increased usage so the amount of traffic or visitors that those search engines could send increased too. It did not take long for site owners to realise that if they could rank well for search terms then they could enjoy much more traffic.
SEO is, and has been from the beginning, the ever changing art of getting listed as near to the top of the first page of search engine results pages (SERP) as is humanly and morally possible. There were always SEO practitioners willing to trick, spam and spoof the engines and, to start with, they did very well from doing so. However, search engines survive by being reliant and soon reacted to block such "SEO cheating" from having any success. However, others know that there is a line between making your site easy to index and spamming the search engines with dirty tricks. The main point being the former is good and the later is bad.
Even today there are people (we call them Black Hat SEOs) that are willing to bend rules and even break them in order to get instant results. These results are often short lived as the domain can quickly become "black listed" or "sand boxed" with the main search engines rendering the SEO effort worthless and spoiling things for any future owner. Other SEOs preferred a more honest and transparent way of working and as a counter to the Black Hat SEOs are known as White Hat SEOs.
As a medium or long term plan White Hat SEO is the only reliable and trustworthy way of working. White Hat SEO (covered in more detail in other sections) focuses on things such as content, keyword density, links structure and even social interaction. In short the best SEO aims to ensure that the content the engine serves is relevant and noticeably so.
These pages explain what SEO is, how it works and why you might want to apply it. If you are are wondering "is SEO for me?" or if you feel you are ready to start SEO there are resources to answer your questions. Once you have covered the basics there is even a list of SEO links and other SEO and SEM resources that you might find interesting and handy.