Что за шаблон Декоратор, и зачем он нужен?

//TODO1: Add abstract class Component
abstract class Component {
    
}

class SalesTicket extends Component {
    public void prtTicket() {
          System.out.println("My ticket");
    }
}
//TODO2: Add abstract class TicketDecorator
//It has Component member, constructor and callTrailer method
abstract class TicketDecorator {
    Component myComponent;
    public TicketDecorator(Component myComponent){
        
    }
    public void callTrailer() {
        
    };    
}
 
 
class Header1 extends TicketDecorator {
    public Header1 (Component myComponent) {
        super(myComponent);
    }
    public void prtTicket () {
        System.out.println("*** Header1 ***");
        super.callTrailer();
    }
}
class Header2 extends TicketDecorator {
    public Header2 (Component myComponent) {
        super(myComponent);
    }
    public void prtTicket () {
        System.out.println("*** Header2 ***");
        super.callTrailer();
    }
}
class Footer1 extends TicketDecorator {
    public Footer1 (Component myComponent) {
        super(myComponent);
    }
    public void prtTicket() {
        super.callTrailer();
        System.out.println("*** Footer1 ***");
    }
}
class Footer2 extends TicketDecorator {
    public Footer2 (Component myComponent) {
        super(myComponent);
    }
    public void prtTicket() {
        super.callTrailer();
        System.out.println("*** Footer2 ***");
   }
}
class Client {
    public static void main(String[] args) {
       //TODO3: Create a decorated sales ticket and print it       
   }
}