Is "composition over inheritance" simply mean "If parent class is never be used except child class, it should be composition"?

I read some posts about "composition over inheritance","where to use composition/inheritance" , "Is-a relationship..." or "Liskov substitution principle" for some time, but I am not sure if I get the right idea about "composition over inheritance".

Alternatively, In my experience, "composition over inheritance" seems just mean "If parent class is never be used except by child class, it should be composition", for example:

public class Parent{
}

public class Child1 extends Parent{
}

public class Child2 extends Parent{
}

If class "Parent" is never appeared at my code other than in Child1 and Child2, then Child1 and Child2 should not be the child class of Parent.

Is that right?