Hey, I think you new here, anyway ..
Search engine optimization is everything that can be done to make a search engine send more traffic to a web site.
Usually this means defining keywords or key phrases and trying to have your web site listed first (or at least near first) for those key terms.
Search engine optimization is usually divided into two categories of tasks:
•   On-page optimization
•   Off-page optimization
On-page optimization is designing your web pages to achieve the best ratings from the search engines.
On-page optimization activites include:
•   Writing keyword-rich text
•   Applying good ALT tags to images
•   Making sure that the web page can be properly "spidered" by all of the search engines
•   Off-page optimization consists of creating inbound links to your web page.