A cookie is a baked or cooked food that is typically small, flat and sweet. It usually contains flour, sugar and some type of oil or fat. It may include other ingredients such as raisins, oats, chocolate chips, nuts, etc.
Cookie is a term used for sweet, flat, baked goods. Biscuit is a term used for a variety of baked, mainly flour-based food products. Cookies are generally sweet. Biscuits are either sweet or savoury. The term cookie is mostly used in American English.