The cashew "nut" is a kidney-shaped seed that grows on a tree not more than 30 feet tall, like an apple or cherry tree, in a double shell at the end of a sweet-smelling pear-shaped fruit called the cashew "apple." These "apples" are not common in the U.S. but are considered delicacies in their native Brazil and Caribbean where they are either eaten raw or their juice is fermented to become alcohol. The tree is a native of South America, but in the 16th century the Portuguese introduced it to East African colonies and India. Today the leading commercial producers of cashews are India, Brazil, Mozambique, Tanzania and Nigeria.
The cashew nut is not as hard as other nuts and has a delicate, sweet flavor. And unlike other nuts, you will never find cashews sold in the store in their shell. The inside of their shell contains a poisonous resin related to the poison ivy family, known as cashew balm which must be carefully removed before the nut can be consumed. (from Planters)