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.
This means when a user clicks a Like button on your page, a connection is made between your page and the user. Your page will appear in the "Likes and Interests" section of the user's profile, and you have the ability to publish updates to the user. Your page will show up in same places that Facebook pages show up around the site (e.g. search), and you can target ads to people who like your content.