In JavaFX, a TextArea is a user interface control that allows the user to enter and edit multiple lines of text. Here's an example of how to create and use a TextArea:

import javafx.application.Application;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.control.TextArea;
import javafx.scene.layout.HBox;
import javafx.scene.layout.VBox;
import javafx.stage.Stage;

public class MyJavaFXApp extends Application {
    
    @Override
    public void start(Stage primaryStage) {
        // Create a text area and a button
        TextArea textArea = new TextArea();
        Button button = new Button("Submit");
        
        // Set the action to be performed when the button is clicked
        button.setOnAction(event -> {
            String text = textArea.getText();
            System.out.println("Text entered:\n" + text);
        });
        
        // Put the text area and button in a layout container
        HBox hbox = new HBox(10, textArea, button);
        
        // Put the layout container in another layout container
        VBox vbox = new VBox(10, hbox);
        
        // Create a scene and set it on the stage
        Scene scene = new Scene(vbox, 300, 250);
        primaryStage.setScene(scene);
        
        // Show the stage
        primaryStage.show();
    }
    
    public static void main(String[] args) {
        launch(args);
    }
}

In this example, we create a TextArea and a Button, and set the action to be performed when the button is clicked using a lambda expression. We then put the TextArea and Button in an HBox layout container, and put the HBox in a VBox layout container. Finally, we create a scene with the VBox layout container and set the scene on the stage. When the user types some text in the TextArea and clicks the button, the program will print the text to the console.