What is Graphics.fillPolygon() in Java?

//import required packages
import java.awt.Graphics;
import java.awt.Color;
import javax.swing.JFrame;
import javax.swing.JPanel;

public class Main extends JPanel {

  public void paint(Graphics g) {

    //set graphics context color
    g.setColor(Color.red);

    
    int xpoints[] = {25, 145, 25, 145, 25};
    int ypoints[] = {25, 25, 145, 145, 25};
    int npoints = 5;
    
    //fill the polygon
    g.fillPolygon(xpoints, ypoints, npoints);
  }

  //main method
  public static void main(String[] args) {

    //Instantiate JFrame
    JFrame frame = new JFrame();

    //add panel
    frame.getContentPane().add(new Main());

    //Will exit the program when you close the gui
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

    //set width and height of the frame
    frame.setSize(200,200);

    //set visibility of the frame
    frame.setVisible(true);
  }
}