paint

public void paint(Graphics g)
{
...
}
invokes a method, called paint.

Every Applet object has a paint method.
A method’s body is contained within braces: { and }.
The paint method is invoked automatically when the applet is executed within a web page.
There is a sequence of methods that are invoked when an applet is executed.
We discuss this applet "life cycle" later.
The paint method has 1 parameter: a Graphics object.
We pass the paint method a Graphics object named g.
When we invoke a method with a particular parameter value, that parameter value is called an argument.
E.g., g is the paint method's argument in our Welcome applet.
I think the term "argument" is excess baggage, but people use this term, so you need to know what they mean.
A method’s parameters/arguments are contained within parentheses: ( and ).
What the paint method does depends on the Graphics object we give it.