Goes to the element selected on the left, and works while the window is covered. Tab is the exception: it is a dialog key, handled by the form and not by the control, so it is sent to the application itself.

The pad is the window, faded. Move across it — the note below says what you are pointing at. A click brings the application to the front first: a real mouse click hits whatever window is on top, and that would be this one.

window