Search Engine Optimization (SEO for short) refers to all of the techniques and practices used to get free traffic from the search engines.
Back in the old days, when dinosaurs roamed the land and Yahoo ruled the internet, the search engines largely directed search queries through website directories. Directory listings would contain descriptions of the websites and various keywords they were relevant for. Inclusion in the most important directories, like Yahoo and Dmoz, was crucial for search engine success.
Then Google came along with a revelation that fundamentally changed the world of search. Google decided to look at the entire internet as a gigantic election. You voted for the best websites by linking to them. However, much like elections in Chicago (where I once worked as an election judge), not all votes were worth the same. The more authority a site has, the more weight Google gives its links. So 1 incoming link from the CNN.com homepage will probably help your site more than 20 links from sites like Virtually Ignorant.
But the strength of the incoming links alone is not enough. There must also be relevance. Despite the fact that CNN is a far more powerful site than Virtually Ignorant, we still outrank them for “Web Design for Beginners.”
So how does Google determine which keywords a site is relevant for and decide how to rank them? There are two important groups of categories, On Page Optimization and Off Page Optimization.
On Page Optimization is simply anything that you control on your website. Important factors include:
The text on the page
The page Title
The page Headings
Rich Media Features like Images and Videos
Off Page Optimization is simply anything done beyond the scope of your website. Important factors include:
How relevant the referring website and webpage are to your site
The anchor text of the link, which are the words that are highlighted in blue