A biscuit is a cookie to us. Tea biscuits are somewhat standardized. There are shortbread, vanilla cremes, burgundies, and digestives. Shortbread is a delightful cookie made in various shapes and made out of flour, butter, sugar, and precious little else -- very rich. Vanilla cremes are round vanilla sandwich cookies to us. Bourbons are rectangular chocolate sandwich cookies. Digestives can be plain, whole grain, chocolate topped (in milk- and semi-sweet chocolate). Digestives are round, flat, and large. Plain digestives can taste just that way.