It's a terminology thing. From the Sun Java Tutorial on nested classes:
Terminology: Nested classes are divided into two categories: static and non-static. Nested classes that are declared static are simply called static nested classes. Non-static nested classes are called inner classes.
Take a look at the page for more info. Also see the tutorial page on inner classes. Lastly, you can look at the Java Glossary's page on nested classes [ August 07, 2008: Message edited by: Mark Vedder ]