In JavaFX, a button is a UI control that can be clicked by a user to trigger an action. Here's an example of how to create a button in JavaFX:

import javafx.application.Application;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.layout.StackPane;
import javafx.stage.Stage;

public class MyJavaFXApp extends Application {
    
    @Override
    public void start(Stage primaryStage) {
        // Create a button with text "Click Me"
        Button btn = new Button();
        btn.setText("Click Me");
        
        // Define what happens when the button is clicked
        btn.setOnAction(event -> System.out.println("Button clicked!"));
        
        // Add the button to a layout container
        StackPane root = new StackPane();
        root.getChildren().add(btn);
        
        // Create a scene and set it on the stage
        Scene scene = new Scene(root, 300, 250);
        primaryStage.setScene(scene);
        
        // Show the stage
        primaryStage.show();
    }
    
    public static void main(String[] args) {
        launch(args);
    }
}

In this example, we create a button with the text "Click Me" and define what happens when the button is clicked using a lambda expression. We then add the button to a StackPane layout container, create a scene with the layout container, and set the scene on the stage. Finally, we show the stage using the show() method.