Is a chestnut and a hazelnut the same thing?

No, a chestnut and a hazelnut are not the same thing. Chestnuts belong to the genus Castanea and are typically larger, with a smooth, shiny brown shell and a starchy, sweet interior. Hazelnuts, on the other hand, are from the genus Corylus, are smaller, rounder, and have a hard, smooth shell with a slightly sweet, nutty flavor. While both are edible nuts, they differ significantly in taste, texture, and botanical classification.