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.

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/