OAuth Basics

This sure looks like a Branded Car Logo . . . Isn't it.
No, this represents the new authentication mechanism on which most of the sites are working today.

OAuth - Open Authentication.

I love Valet key example. Many luxury cars come with a valet key. It is a special key you give the parking attendant and unlike your regular key, will only allow the car to be driven a short distance while blocking access to the trunk and the onboard cell phone. Regardless of the restrictions the valet key imposes, the idea is very clever. You give someone limited access to your car with a special key, while using another key to unlock everything else.