so if you have ever used facebook you know at the top of the page you will see a search bar and if you start to type in any keyword for this example im going to use the word "bike shop" so if you type into the search bar bike shop you will see the fan page with the most "likes" this is all that matters to the facebook search engine so having tons of facebook likes will clime you to the top of the facebook search engine.
So say you own a website for selling bikes wouldn't you want to be at the top of the facebook search engine?
All you have to do is make a facebook fan page and get tons of likes and you will start to see 100s of people per day come to your website from your facebook fan page.
One more tip is to have your facebook fan page with a username do this by going to your fan page and clicking the edit page button. Now on the left side you will see basic information click that and you will be able to give your fan page a username url so your facebook page page will look like this facebook.com/yoursite instead of facebook.com/yoursite/4395803809
This will improve your google search results and be easier for people to remember your fan page url