Beginning Flutter: 07 Container Widget
Container widgets do not have any visual properties by themselves. They contain a child widget, and the child widget is what is rendered on the mobile app. The container widget is among a series of wrapper widgets, that gives form/location to its child widget. If you did not use a wrapper widget like Container, the system would not know where to draw the child widget.
padding is the property to determine where the child widget is located with respect to the sides of the mobile device. I don't have the complete grasp of padding just yet. Maybe that's a future video.