IBOutlet is a special instance variable that references another object.
A message can be sent through an outlet. Interface Builder recognizes them.
IBAction is a special method triggered by user-interface objects. Interface Builder recognizes them.
IBOutlet id textField;// links toTextField UI object
-(IBAction)doAction:(id)sender;// e.g.called when button pushed
File Owner –
The File Owner is an instantiated, runtime object that owns the contents of your nib and it’s outlets/actions when the nib is loaded.
The owner parameter is particularly important. That’s the runtime instance of a class that owns the contents (outlets, actions andobjects) of the nib being loaded.
First responder –
First responder is simply the first object in the responder chain that can respond to events. The responder chain is a runtime collection (or more accurately a hierarchy) ofobjects that can respond to an event.