Facebook callback URL

I am a little confused with the Facebook call back URL. I am building a iPhone application with Facebook login. So I will receive the access token from Facebook after the user logged in. Then I save this access token to my local (server side) DB. After that I want to use this access token to sent for example a post via C#.

What should I define for the callback URL? What is the开发者_如何学C importance of this?

The callback url is used to provide fast app switching, that is, the user of your app is first redirect to facebook app or site to do the login, then it invokes the url you did define and, if properly configured, it will be redirected to your app again. You can specify the callback url from developers section on facebook, then you have to support it in the your app plist.