Cornstarch is produced from the endosperm located in the middle of the corn kernel. The starch is the powder form of the endosperm inside the corn kernel hence it is called as cornstarch. It is not at all similar to corn flour.
Mainly, this fine white powder is used as a thickening agent in soups and sauces, also it is used to coat the veggies or meat before deep frying for a crispy texture.