Marker Interfaces- A marker interface is one which has absolutely nothing in them.They have no methods or variables.They are used to give permission to a class to execute a particular functionality.

Interface M{
}

Examples are Cloneable Interface,remote Interface,Serializable Interface etc.

We know that we have a clone method in which we can clone an object i.e make a bit by bit copy of an object.But to make a clone of an object the class should implement the Cloneable Interface to have permission to make Clone objects.

Now let us see what clone method does

A a2= new A();

So here both a1 and a2 point to 2 different objects of A i.e to two diff memory locations where content of members corresponding to these two different objects iss stored.Now let us do one thing

a2 = a1;

Now a2 will start pointing to the same object or the memory location to which a1 is pointing to.

But if we now do

a2 = a1.clone();

This will create a new memory location and a2 will start pointing to this new memory location and all the content of member variables corresponding to objectof class A to which a1 was pointing to will also be COPIED to this memory location as well.