Just a few short years ago, there was a web page description tag called the Meta Keywords tag. It quickly became popular with unscrupulous web masters incorrectly applying keywords in an effort to rank better in the search engines. Google, and many top search engines ended up discounting, and ultimately ignoring keywords. It is still important to include this in your page, but for different reasons.
Increasingly, search engines have been placing more importance on a websites 'connectivity' to other websites to determine how important, or relevant, your site is. This connectivity is done through linking. A link is like vote of confidence (in the eyes of the search engine) that says, "This site counts." The more links you have coming into your site means the more 'votes of confidence' that your site is worth a visit. Majority rules, democracy in action!