show() is just a convenience function for setVisible(true).
Similarly hide() is equivalent to setVisible(false)
Internally, the same code is used to render your view.
as an example. According to it,
void QWidget::show () [slot] Shows the widget and its child widgets. This function is equivalent to setVisible(true).
You'll find lots of such functions in Qt to just make things more intuitive, especially when it comes to widgets and views.