Cornmeal is flour ground from dried corn, and is a common staple food. In the United States it is also called cornflour. (In the United Kingdom, cornflour is used to mean cornstarch.)
Stone ground cornmeal retains some of the hull and germ, lending a little more flavor and nutrition to recipes. It is more perishable, but will store longer if refrigerated.
White cornmeal (mealie meal) is more traditional in Africa. It is also popular in the Southern United States for making cornbread. Blue cornmeal is made from the rarer blue corn or by adding blue food coloring.