What is Search Engine Optimisation?
The concept itself is not hard to grasp. We can basically define SEO as a group of strategies that you can apply in order to make your website relevant to the users of a search engine, making it easy for people to find what you offer (you can check more about SEO and SEM in the article: SEM / SEO / Paid search advertising – How does it all come together?).
If you are a beginner, take a look at this great video from the guys over @searchengineland: