Cashew nuts are actually seeds that adhere to the bottom of the cashew apple, the fruit of the cashew tree, which is native to the coastal areas of northeastern Brazil. Cashew apples, while not known in the U.S., are regarded as delicacies in Brazil and the Carribean. The seed we know as the kidney-shaped cashew "nut" is delicate in flavor and firm, but slightly spongy, in texture. You have probably noticed that cashews in the shell are not available in stores. This is because these nuts are always sold pre-shelled since the interior of their shells contains a caustic resin, known as cashew balm, which must be carefully removed before they are fit for consumption. This caustic resin is actually used in industry to make varnishes and insecticides. Cashews, known scientifically as Anacardium occidentale, belong to the same family as the mango and pistachio nut.