Ashwagandha is sometimes called Indian ginseng, not because it's related botanically (it's closer to potatoes and tomatoes), but because its traditional uses were similar. Like ginseng, ashwagandha was thought to be a "tonic herb" capable of generally strengthening the body. On this basis it has been used in hopes of prolonging life, improving overall health, enhancing mental function, increasing fertility and libido, augmenting physical energy, and preventing infections.
In addition, as its species name somniferumsuggests, ashwagandha been used traditionally for inducing sleep.
A typical traditional dosage of ashwagandha is 1 to 2 g of the root (boiled in milk or water for 15-20 minutes) taken 3 times daily.