What is the difference between coding a class object in its reference type and the parent reference type

I have three classes

public class Abc
{
    public methAbc()
    {
        System.out.println("parent class method");
    }
}


public class Xyz extends Abc
{
    public methAbc()
    {
        System.out.println("overriden parent class method");
    }

    public methXyz()
    {
        System.out.println("child class method");
    }
}

class Pqr
{
    Xyz childObjChildRef = new Xyz();
    Abc childObjParentdRef = new Xyz(); 
}

in the Pqr class what is the main difference in creating objects in different links

1: when holding an object in the same class reference ==>, then we can call all methods from the class

2: when holding an object in the link of the parent class ==>, then we can only call the overridden methods from the class