If you have a facebook page, badges are simply links to that page.
E.g if you have a website or blog, you can add a badge(most commonly facebook logo) and it show your visitors that you have a facebook presence as well.
You visitors can click on the bad to automatically "like" your content, or it can display your latest status updates/pics, join your facebook page and so on. Different badges for different type of things you want to show/achieve.
You just need to add 1 line of code to your website/blog for that.