From what I can understand from the definition in wikipedia. They are one & the same and are used liberally in puddings. Read below:
Cornstarch, or cornflour, is the starch of the maize grain, commonly known as corn. It is also ground from the endosperm, or white heart, of the corn kernel. It has a distinctive appearance and feel when mixed raw with water or milk, giving easily to gentle pressure but resisting sudden pressure. It is usually included as an anti-caking agent in powdered sugar (10X or confectioner's sugar). For this reason, recipes calling for powdered sugar often call for at least light cooking to remove the raw cornstarch taste.