Field corn and sweet corn belong to the same botanical species, but they are bred, harvested, and used very differently. Sweet corn is the type normally served on the cob or sold frozen and canned. It contains genetic traits that allow more sugar to remain in the kernels, giving it a tender texture and naturally sweet flavour.

Farmers harvest sweet corn while the kernels are still immature, plump, and milky. It is best eaten soon after picking because its sugars gradually convert into starch, reducing its sweetness and tenderness.

Field corn, often called dent corn, stays on the plant much longer and is harvested only after the kernels become hard and dry. It contains more starch and far less sugar at maturity, so biting into an ear straight from the field would usually be tough and bland rather than sweet. Most field corn is not sold as fresh corn on the cob. It is commonly processed into animal feed, cornmeal, cereal, starch, corn oil, sweeteners, ethanol, and many other products. Although it is safe to eat when properly processed, it is not bred for the same fresh flavour and texture as sweet corn.

So, your husband is right that they are different, but they are still very close relatives. Sweet corn was developed primarily for eating fresh as a vegetable, while field corn was bred mainly as a dry grain for processing and other uses.