Close Window ⌘W
Close the frontmost (focused) window.
Only one window can have key focus at a given time, this is called the active window. When several normal windows overlap, the active window is the window in the foreground. The title of the window with key focus is black (the titles of other open windows are gray). Inside a window, the area with key focus (for example, the Tracks area) is bordered by a blue frame.