The tuberous underground roots are called rhizomes and they are actually modified stems. They divide into palmate shapes and have greenish-yellow insides, protected outside by a tannish skin. The young rhizomes are tender and succulent and great for preserving. The more mature roots are a useful medicine. They are peeled and dried in the sun before they are shipped out for medicinal use around the world.
Medical ginger is an aromatic stimulant that is useful for indigestion and fever.
We also know the edible ginger as an enhancement in cooking. For stomach upsets due to bumpy travel, wild sailing or morning sickness, ginger ale and ginger tea are winners. My niece had horrible morning sickness for more than four months. It takes about 10 months to grow ginger from planting to harvest of the roots. When the leaves wither down to the ground, it is time to harvest.