Wikipedia says that "a biscuit is a hard baked sweet or savoury product like a small, flat cake, which in North America may be called a "cookie" or "cracker". The term biscuit also applies to sandwich-type biscuits, where a layer of 'cream' or icing is sandwiched between two biscuits.
"Sweet biscuits are commonly eaten as a snack and are generally made with wheat flour or oats and sweetened with sugar or honey. Varieties may contain chocolate, fruit, jam, nuts or even be used to sandwich other fillings. There is usually a dedicated section for sweet biscuits in most UK supermarkets. In Britain, the digestive biscuit and rich tea have a strong cultural identity as the traditional accompaniment to a cup of tea, and are regularly eaten as such. Many tea drinkers "dunk" their biscuits in tea, allowing them to absorb liquid and soften slightly before consumption."