It means that you need to know the details before assuming what it means.
4.0 unweighted GPA means that all grades are A grades.
But many people say “4.0 GPA” not specifying whether it is weighted. And weighting methods vary, so that a 4.0 weighted GPA may be from a 3.0 or lower unweighted GPA if the weighting system is an exaggerated one.