Difference between Open ID and OAuth

Question

i am familiar with OAuth but not with open id.

 

Nowadays many web site allow us to login to their site with facebook, linkedin etc. so when we click on facebook image then we redirected to facebook login page where we provide our facebook credential. if  credential is right then facebook redirect us to first site. the advantage is we do not have to create & remember many credentials rather remember one.

 

but i do not know what is open id and how it works? i read this article http://www.devcurry.com/2012/11/aspnet-mvc-4-external-login-using-openid.html

 

it seems that in case of both open id and oauth user create their login to external site and user use that credential to other web site to login. if it is right then oauth and open id both are same and doing same purpose. so where is the difference?

 

please discuss how open id is different from oauth in terms of flow ?