How does OpenID authentication work?

Question

I am a little curious to know about how OpenID authentication works.

Is there any difference between OpenID authentication and the authentication which sites use exc

Answer 1

I stumbled across this great OpenID introduction which is neither too high-level nor too low-level.

http://wiki.openid.net/w/page/12995171/Introduction

It's a bit verbose, and more or less written as prose, but it's a fun read and very informative about what happens behind the scenes.

(Answer pasted from my answer at OpenID login workflow?.)