A peanut is actually not a nut, but a legume (or a bean). A cashew is a tree nut typically grown in tropical climates. They're both buttery-tasting and a bit sweet and make excellent butter when ground. Cashews are a good substitute for people with peanut (but not general nut) allergies.

Peanuts are a legume as opposed to a tree nut because they grow underground. Cashews are a nut but are lower in fat than a peanut. Peanuts are higher in protein, however.