What is Google Authorship?

A markup setup that links a piece of content to its real-person author's Google Plus profile, causing the author's avatar to appear in search results next to the article.

From Google Authorship Tips - Internet Marketing Podcast Number 204

A system where content creators claim ownership of their work by setting up a Google+ profile, adding contributor links, and tagging posts with rel equals author so Google attributes the content to them.

From Content Optimization Tips - #SEOpodcast 237

A setup linking content to a Google Plus author profile; the episode notes authorship visibility improves when the author is actively posting, sharing, and getting plus ones on their personal Google Plus page.

From Hashtagging Your Website - #SEOpodcast 228

A setup that lets content creators claim their original content so Google associates it with them, displays their avatar in search results, and can increase click-through rates.

From Online Marketing and SEO Trends - Internet Marketing Podcast Number 209

A setup linking your Google Plus profile to content you publish, allowing Google to display your avatar next to search listings, claiming ownership of that content and helping prevent duplicate content issues.

From Enhancing your Reviews on Google+ - Internet Marketing Podcast Number 208

A configuration linking a Google Plus profile to website content using a rel equals author tag, which can display the author's avatar in search results if the G Plus account is actively used.

From 2013 SEO Year End Review - P2 - #seopodcast 219