In the Southern United States
means a form of bread
similar to a roll made with baking powder or baking soda as a rising agent rather than yeast
(rolls made with yeast are often called "yeast rolls" to distinguish them, and biscuits and corn bread are sometimes referred to collectively as "quick bread")
A basic biscuit recipe includes flour, shortening (often lard), baking powder or soda, and milk (buttermilk or sweet milk). Common variations involve cheese or sugar.
In Europe, a biscuit is a harder baked product which in North America would be called a "cookie". The origins of the word mean twice cooked.