According to the US Forest Service, true nuts are "dry, single-seeded fruits that have high oil content. They are usually enclosed in a leathery or solid outer layer. In botany terms, nuts are strictly a particular kind of dry fruit that has a single seed, a hard shell, and a protective husk." So, what you likely consider nuts might actually fall into many different categories including seeds, legumes, and drupes. Because peanuts are a pod of seeds that grows underground, they are legumes. A drupes, on the other hand, is a "fruit with a hard stony covering enclosing the seed (like a peach or olive) and comes from the word drupa meaning overripe olive." Walnuts, pistachios, pecans and almonds are all the seeds of drupe fruits. Hungry for more on your favorite snack? We've collected some great videos about nuts, how to make them, and why they've become the culprit of so many allergy attacks.