HBox is a JavaFX layout container used to arrange UI components in a horizontal row. It arranges the child nodes in the order in which they are added to the container, and it allows developers to specify the spacing between the nodes.

Here is an example of using HBox to arrange two Button components:

HBox hbox = new HBox();
Button button1 = new Button("Button 1");
Button button2 = new Button("Button 2");
hbox.getChildren().addAll(button1, button2);

// Set the spacing between the buttons
hbox.setSpacing(10);

// Add the HBox to a parent container
Scene scene = new Scene(hbox, 300, 100);

In this example, an HBox container is created, and two Button components are added to it using the getChildren() method. The setSpacing() method is called to set the spacing between the buttons, and then the HBox is added to a Scene object.

By default, an HBox will lay out its child nodes so that they are centered horizontally within the container. However, you can use the setAlignment() method to specify a different alignment for the children, such as Pos.CENTER_LEFT, Pos.CENTER_RIGHT, or Pos.TOP_LEFT.

HBox is a simple and effective way to arrange UI components in a horizontal row, and it can be used in a variety of different applications, from simple forms to complex user interfaces.