What does the access_token in the following facebook graph request means? and how to get it?

I want to show the list photo's or album's of a facebook user in my iphone app, where in he should be able to save those photo's to photo galleray. I found some examples foe 开发者_Python百科php but unable to reproduce the same in iphone ASIRequest. I want to use following graph request so how do i the access_token in session object.

 https://graph.facebook.com/me/albums?access_token=   //GraphRequest
// This is the delegate i end up with after the user login, currently i'm querying some fql, 

- (void)session:(FBSession*)session didLogin:(FBUID)uid {
    _label.text = @"";
      NSString* fql = [NSString stringWithFormat:
                     @"select uid,name from user where uid == %lld", session.uid];
    NSDictionary* params = [NSDictionary dictionaryWithObject:fql forKey:@"query"];
    [[FBRequest requestWithDelegate:self] call:@"facebook.fql.query" params:params];
}

Or is there any work around to meet my requirement? thanks in advance.

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You need to first authenticate which will get you the access code. You then use that access code for subsequent communication.

http://developers.facebook.com/docs/authentication/