What is the difference between a nested static class and a nested non-static class?

A static nested class does not have access to the non-static members of the outer class and does not require an instance of the outer class to be created.

An inner class (non-static nested class) has access to all members of the outer class, including private ones, and requires an instance of the outer class to be created, as it implicitly holds a reference to the outer class instance.