Maize is a tall farm plant. Its seeds — usually yellow, sometimes white — grow tightly together on a cob, a hard long core, and we cook those seeds as food. In British English, and in science and farming around the world, maize is the usual name. In American English people almost always say corn for the same plant — though actually in British English corn can mean grain in general, such as wheat, so the two words do not line up perfectly. Europe did not have this plant until after contact with the Americas. You meet it as sweetcorn on the cob, as popcorn, as breakfast flakes, or ground into flour; farmers also grow it to feed animals. It is an ordinary food-and-farming word, not a fancy one.