Facebook "Like Button" Why it is important it add it to your site and blog

The Like button lets a user share your content with friends on Facebook. When the user clicks the Like button on your site, a story appears in the user's friends' News Feed with a link back to your website.
When your Web page represents a real-world entity, things like movies, sports teams, celebrities, and restaurants, use the Open Graph protocol to specify information about the entity. If you include Open Graph tags on your Web page, your page becomes equivalent to a Facebook page.