"cashew, almond, and pistachio plants are not true nuts, but are rather classified as "drupes." Drupes are fruits that are fleshy on the outside and contain a shell covering a seed on the inside. What we consume is this seed. The classification of walnuts and pecans is not as clear cut— they have characteristics of both nuts and drupes, but don't completely fulfill the criteria for either. Some refer to them as "nut-like drupes", others as "drupaceous nuts". Interestingly, peaches and mangoes are also drupes—except in this case, we eat the fleshy exterior and not the shell and seed found inside it. Confusing, isn't it?"