In Britain corn generally refers to wheat. However, in the US, the corn refers to maize, Zea mays . Popping corn and sweetcorn are just two of the many varieties of maize grown commercially. Each variety has different properties and is grown for different reasons. The bulk of tissue within a grain of corn is called the endosperm.
Endosperm is specialised storage tissue providing nutrients for the embryo when the seed germinates.
It is also a source of carbohydrate for humans. In popcorn, Z. mays var. everta, the outer part of the endosperm is hard but the centre is soft. Sweetcorn, Z. mays var. It is grown in the US and Europe as a vegetable, as well as in Mexico and South Africa where it is used in brewing beer. Sugars enter the developing seed and are converted to starch.