Search engine optimisation is the process by which web page designers and copy writers structure the layout and content of web pages so that search engines place those pages at the top of search results when certain keywords are entered. This means that more people are likely to click on those links and read those pages.
For example, my web pages have been optimised for the following keyword combination: brisbane web design . If you go to Google and use those key words, you will probably find my web site will appear in the top 10 sites listed. Basic on-site SEO is included in all web design packages.