So it is a 2 step verification service that uses an app on a phone:
"Typically, users will install the Authenticator app on their smartphone. To log in to a site or service that uses two-factor authentication, they provide user name and password to the site and run the Authenticator app which produces an additional six-digit one-time password. The user provides this to the site, the site checks it for correctness and authenticates the user."
I have never used it before. Do a lot of sites use it?
One of the Geeklog Core Developers.