Understanding Swift 2.2 Selector Syntax - #selector()

I am switching over the syntax of my project toward Swift 2.2 (which xCode helps me do automatically); however, I do not understand the new #selector() syntax.

As an example:

timer = NSTimer.scheduledTimerWithTimeInterval(1.0, target: self, 
             selector: #selector(MyVC.timerCalled(_:)), //new selector syntax!
             userInfo: nil, repeats: true)

This has the selector #selector(MyVC.timerCalled(_:))

What does the _: signify? Can you add other variables into this selector? Say, #MyVC.timerCalled(_:whateverVar).
General info on what is different in this syntax as opposed to the string based implementation from earlier versions of Swift are greatly appreciated.

Thanks in advance

Understanding Swift 2.2 Selector Syntax - #selector()