GridBagLayout is a flexible layout manager provided by Java's Swing framework. It is used to arrange components in a grid of rows and columns, with the ability to span rows and columns, and align and distribute components within each cell.

GridBagLayout is very powerful and can produce complex layouts, but it can also be difficult to use due to its complexity. It is best suited for situations where the layout is not easily expressed using simpler layout managers.

Here's an example of how to use GridBagLayout to create a simple layout with two buttons:

import java.awt.*;
import javax.swing.*;

public class GridBagLayoutExample {
    public static void main(String[] args) {
        JFrame frame = new JFrame("GridBagLayout Example");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        JPanel panel = new JPanel(new GridBagLayout());
        GridBagConstraints c = new GridBagConstraints();

        // Add the first button
        JButton button1 = new JButton("Button 1");
        c.gridx = 0;
        c.gridy = 0;
        c.insets = new Insets(10, 10, 10, 10);
        panel.add(button1, c);

        // Add the second button
        JButton button2 = new JButton("Button 2");
        c.gridx = 1;
        c.gridy = 0;
        panel.add(button2, c);

        frame.add(panel);
        frame.pack();
        frame.setVisible(true);
    }
}

In this example, we create a JFrame and a JPanel with a GridBagLayout. We then create a GridBagConstraints object, which is used to set the position, size, and alignment of each component. We add two JButton components to the JPanel, and specify their positions and other constraints using the GridBagConstraints. Finally, we add the JPanel to the JFrame and display it.

This code will produce a window with two buttons arranged side by side, with some margin around them. The GridBagConstraints can be used to control many aspects of the layout, such as component size, alignment, and spanning. The documentation for GridBagLayout and GridBagConstraints provides more information on how to use them.