all the time. Sweet corn is the type of corn you eat as corn on the cob or canned corn or frozen corn. It has relatively small ears and small kernels. And it's very sweet to the taste.

Field corn is just a larger, less sweet, variety of corn. The stalks grow to 8' to 10' tall. The ears are often 14" to 16" long. If you pick it young, it's somewhat sweet, and you can eat it off the cob raw, although it's definitely not as tasty as sweet corn. Field corn is usually harvested dry, with the kernels hard. Basically you grow the corn and let the stalks turn brown and dry up. The ears dry up and the kernels are hard. This allows the components of the combine to rub the kernels and separate them from the cob.

Field corn is used for both human and animal consumption. It's ground into meal or flour and turned into corn meal or cereal ingredients. It's cracked and turned into animal feed. It's used in pet food, including dog food and cat food. The oils can be separated during processing, from which you get vegetable oil (corn oil). Any processed corn product humans eat (corn meal, corn cereals, corn chips, corn tortillas, etc) are made with field corn.