what is the difference if i return "YES" or "NO" when i call textFieldShouldReturn

This is the text field delegate method but i have doubt about return type

-(BOOL)textFieldShouldReturn:(UITextField *)textField
{
  [textField resignFirstResponder];

   return NO;
}  

and this is the same method with different return type

-(BOOL)textFieldShouldReturn:(UITextField *)textField
 {
   [textField resignFirstResponder];

   return YES;
 }

by both we can hide key board in i phone . but what is the meaning of return type "YES" or "NO". I am not seeing any difference.