How UITableView delegates works?

How UITableView delegates works?

In my view I have used UITableView, I have set delegate and data source
with file owner in nib. And in my class .h file I have conforms to the
protocol like below...
eg:
@interface test : UIViewController<UITableViewDelegate,
UITableViewDataSource>
{
...
...
}
Everything works fine... delegate methods are all called properly... Now
my question is why we are adding "UITableViewDelegate,
UITableViewDataSource" in .h. without that also I'm getting those calls.
What is the use of this?
thanx