Deciduous means seasonal. A deciduous tree sheds all its leaves as seasons change and grows some new ones when seasons change again.
Many trees are deciduous. They shed their leaves to adapt to the changing weather conditions. In some parts of the world trees shed their leaves as the weather becomes colder and the ground freezes. In other parts of the world trees shed their leaves because the weather has become hot and dry. In both freezing ground or dry soil there is little water for the tree roots to take in. Deciduous trees have broad leaves which need large amounts of water to make food. If the water is not available in the soil the trees shed their leaves and live off the food stored in their wood. When the weather changes and there is water in the soil the deciduous trees sprout new leaves.