Corn is a grain as well as a vegetable. It grows within a tall grass-like stalk and produces large kernels on a cob. The kernels of corn can range from white to yellow. "Indian Corn" has kernels that are a mix of yellows, oranges, browns, reds, and purples.
Popcorn is actually a type of corn where the kernels "pop" open when heated.
Corn is one of the few crops that can be used for hundreds of different things. It can be used for food for humans and livestock. It can also be used as fuel to power tractors, trucks, and other farm equipment. It is also used in hundreds of products such as chewing gum, toothpaste, crayons, shoe polish, and even tires.