Chestnuts belong to the family Fagaceae, which also includes Oaks and Beeches. There are four main species commonly known as European, Chinese, Japanese, and American chestnuts.1
The name "chestnut" is derived from an earlier English term "chesten nut", which descends from the Old French word 'chastain' (Modern French, 'châtaigne'). The chestnut season is brief, but whole peeled chestnuts, either canned, or vacuum-packed, are available from major supermarkets. Dried chestnuts are also available from health food stores, but must be soaked in water overnight then simmered before use.
Fresh chestnuts must always be cooked before use and are never eaten raw, owing to their tannic acid content. You need to remove the chestnuts from their skins by either boiling or roasting them. For both options, first make a small incision in the skin or you'll have a house full of chestnut shrapnel as they will explode. If cooking over an open fire, keep one whole as when this explodes you know the others are done (not a method for the overly house proud!).
Once cooked, peel off the tough shell and the papery thin skin underneath. Peel the nuts whilst hot (it's impossible to peel a cold chestnut!) to ensure the complete removal of the inner brown furry skin, called the 'tan', which is bitter.2
"Chestnuts are quite different from other nuts nutritionally and in a culinary sense. They are only eaten cooked and have a sweet, nutty taste but a texture similar to a firm baked potato rather than the crunchy texture of other nuts. Nutritionally chestnuts are more like a wholegrain than a nut as they are low in fat, contain carbohydrate and are high in dietary fibre. They are also a source of folate and surprisingly contain vitamin C which is not found in other nuts, its no wonder they have just scored a full 5 stars on the health star rating!" 3
REFERENCE: Wikipedia.1 - BBC Goodfood.2 - Chestnuts Australia.3