Among the most frequently-asked questions we get at the Google Authorship and Author Rank Community on Google+ are those concerning the usage of rel=authorship and rel=publisher connections.
Or to put it another way, should your site have an Authorship connection to Google+, a Publisher connection, or both? And for what is each intended? To what parts of your site should each be applied?
Read more to understand the difference between the markup tags rel=author and rel=publisher, and where and how to use each properly.