Kind of an old video, but here is a rel=”author” description and implementation as told by a couple of developers from Google geeking out over HTML 5 design standards. That markup needs to be added to a link to your Google+ profile from your site, and your profile needs to show that you are a contributor to that specific domain.
There is also a rel=”publisher” for organizations and businesses, difference being the link is to a Google+ Page not a personal profile.
Links are becoming more semantic, weighted towards quality over quantity, and profiles are key. Especially your Google+ profile. Duh, you should have seen that one coming.
UPDATE: Still not sure? Here’s Matt and Othar one more time.