What does the protected modifier mean?

Yes, protected members can be accessed from the class itself, subclasses of the class and also all classes in the same package of the class (doesn’t matter if those are subclasses or not). If you didn’t know that last part before, then you’ve just learned something new.

It simply means that you can use those members; if a member is not accessible, it means you’ll get a compiler error when you try to use it.