A cookie is a baked or cooked snack or dessert that is typically small, flat and sweet. It usually contains flour, sugar, egg, and some type of oil, fat, or butter. It may include other ingredients such as raisins, oats, chocolate chips, nuts, etc.
Most English-speaking countries call crunchy cookies biscuits, except for the United States and Canada, where biscuit refers to a type of quick bread. Chewier biscuits are sometimes called cookies even in the United Kingdom. Some cookies may also be named by their shape, such as date squares or bars.
Biscuit or cookie variants include sandwich biscuits, such as custard creams, Jammie Dodgers, Bourbons and Oreos, with marshmallow or jam filling and sometimes dipped in chocolate or another sweet coating. Cookies are often served with beverages such as milk, coffee or tea and sometimes “dunked”, an approach which releases more flavor from confections by dissolving the sugars, while also softening their texture. Factory-made cookies are sold in grocery stores, convenience stores and vending machines. Fresh-baked cookies are sold at bakeries and coffeehouses.
Info and image from Wikipedia