The hazelnut also known as the filbert, is a type of nut that comes from the Corylus tree. Hazelnuts have a sweet flavor and can be eaten raw, roasted or ground into a paste. Like other nuts, hazelnuts are rich in nutrients and have a high content of protein, fats, vitamins and minerals. hazelnuts are encased in a smooth, hard brown shell but are most commonly sold shelled. The sweet-tasting, cream-coloured kernel is small and round, with a pointed tip. Its thin, dark brown skin is faintly bitter, so some people like to remove this before eating. It Also known as cobnuts or filberts, like almost all nuts, they have a high fat content, which means they will go rancid pretty quickly if not refrigerated.