Deciduous is a term given to trees and shrubs that lose all their foliage for at least part of the year.
For most deciduous plants in temperate areas, all foliage is dropped in the fall. New foliage sprouts in the spring.
In many arid regions, deciduous plants lose their leaves during the dry season.
Dropping their leaves in fall is not a bad sign. The plant is conserving energy and food, and redirecting it below ground to the root system.