In JavaFX, the Line class is used to create a line shape that connects two points. A line is a basic geometric shape that can be used to draw straight lines of varying lengths and orientations.

Here's an example of how to create and use a Line in a JavaFX application:

import javafx.application.Application;
import javafx.scene.Scene;
import javafx.scene.layout.Pane;
import javafx.scene.paint.Color;
import javafx.scene.shape.Line;
import javafx.stage.Stage;

public class MyJavaFXApp extends Application {

    @Override
    public void start(Stage primaryStage) {
        // Create a new Line object with starting and ending points
        Line line = new Line(10, 10, 100, 100);
        line.setStroke(Color.RED);
        
        // Add the line to a Pane layout
        Pane layout = new Pane(line);
        
        // Create a Scene object with the layout and set it on the stage
        Scene scene = new Scene(layout, 300, 200);
        primaryStage.setScene(scene);

        // Show the stage
        primaryStage.show();
    }

    public static void main(String[] args) {
        launch(args);
    }
}

In this example, we create a Line that starts at point (10, 10) and ends at point (100, 100). We set the stroke color of the line to red using the setStroke() method. We then add the line to a Pane layout, and set the Pane as the root of the Scene. Finally, we display the scene on the stage using the show() method.

The Line class provides a number of methods for configuring the appearance and behavior of a line. You can set the stroke width and color of the line, add arrowheads at the start or end of the line, and set the line to be dashed or dotted. You can also use the setOnMousePressed() and setOnMouseReleased() methods to add event handlers that respond to user input.