Java - Duda con paintComponent

Estoy comenzando con el tema de swing y awt, y me surge la siguiente duda:

¿En este método que es lo que estoy haciendo?

Estoy usando un metodo llamada paintComponent que recibe como parametro un objeto de tipo Graphics, esto si, ¿ Pero que se supone que se esta haciendo con el super.paintComponent? Estoy llamando al mismo método dentro de otro que sobrescribe al mismo ...No entiendo.

Y ¿ por qué no te lees un tutorial, o algo, antes de empezar ?

https://docs.oracle.com/javase/tutorial/uiswing/painting/index.html

Copio y pego:

The paintComponent method is where all of your custom painting takes place. This method is defined by javax.swing.JComponent and then overridden by your subclasses to provide their custom behavior. Its sole parameter, a java.awt.Graphics object, exposes a number of methods for drawing 2D shapes and obtaining information about the application's graphics environment. In most cases the object that is actually received by this method will be an instance of java.awt.Graphics2D (a Graphics subclass), which provides support for sophisticated 2D graphics rendering.

Most of the standard Swing components have their look and feel implemented by separate "UI Delegate" objects. The invocation of super.paintComponent(g) passes the graphics context off to the component's UI delegate, which paints the panel's background. For a closer look at this process, see the section entitled "Painting and the UI Delegate" in the aforementioned SDN article.

Porque estoy siguiendo un curso gratis, y el no lo explica....