The document describes how to create a simple "Hello World" Mule application using Mule 4. The steps include:
1. Creating a new Mule project in Anypoint Studio
2. Dragging and dropping an HTTP Listener connector onto the canvas
3. Configuring the listener to receive requests on port 8081
4. Adding a logger to log a message on request receipt
5. Configuring the listener response directly to return the message "Hello World Response"
6. Running the application and testing it using Postman to return the response message.