IBAction and IBOutlet keywords

(IBAction)selectedCard:(UIButton *)sender {

IBAction is nothing but typedef void. Xcode puts this to keep track that this not a random method that returns void but an Action method that connects view to the controller.

@property (weak, nonatomic) IBOutlet UILabel *selecedLabel;

IBOutlet is typedef of void. Xcode puts this just to keep track that it not some random @property, but it is an Outlet i.e. connection to the view.