Okay...WHAT exactly is SEO (Search Engine Optimization)? Is it writing code? Is it programming? Web design? Can someone please clarify?

Because I know nothing about computers and the internet, the Wikipedia page on SEO pretty much leaves me more confused than I was before.

What is it search engine optimization? It’s optimizing the chances that your website will be among the first results when you google it? How do you do that? Is it just editing the HTML code so that it’s filled with a bunch of keywords?

Is it diffuclt? Is it easy? Why? Is it a skill that I should know as I try to break in to the marketing/advertising world? How long does it take to learn?

All answers are appreciated – thanks a million.