Objective C: what is a “(id) sender”?

Question

In some IBAction I saw:

- (IBAction)pushButton:(id)sender;

This (id)sender when do I use it?

Answer 1

Here's an example of (id)sender passing tag information from several buttons to one IBAction. This video demonstrates the concept of (id) sender in action, which I found to be very useful.

iPhone Programming - (id)sender explained