ok thanks you for your comments. just reply some comment that raider pointed out.
"How does a visitor find your link in the directory from the Yahoo main page?...That's what I'm getting to."
SEO is long run, it helps you getting top rank in google, yahoo or msn when user type in a keyword say "domain name registration" (for a new site to have this keyword rank high is really hard). so buy submitting your website to some authority site (in the thread's example) it's yahoo. your website can eventually rank higher and when some want to register your domain and found your site in top ranking, they will look at it and see what's good about your site and eventually your site got traffic or sales conversion.