This user chose to "Post as a guest" rather than [registering][1] an account. The name shown is the name they gave at the time they posted.

Such users haven't set a password, verified an email address, etc., and are only authenticated via a browser cookie. If the cookie is lost, the user can no longer edit or accept answers to their posts.

See also: [Why should I register my account?][2]


  [1]: http://serverfault.com/help/why-register
  [2]: https://meta.stackexchange.com/q/44557/189912