White corn is corn (maize) with pale white kernels rather than the more common yellow; the term describes kernel color and spans multiple corn types, including sweet corn, field corn, and flour/dent corn, so it isn't a synonym for 'sweet corn' specifically.
Maize was domesticated from wild teosinte in Mesoamerica roughly 9,000 years ago, long before the Olmec, Maya, and Aztec civilizations that later made corn central to their diets; corn agriculture spread from there across the Americas.
Today white corn is grown commercially in the United States (notably the Midwest and parts of California), Mexico, and South America. It's ground into masa for tortillas and tamales in Mexican and Central American cooking, used for grits, succotash, and cornbread in the American South, and appears in corn soups and other dishes in parts of Asia.
As fresh sweet corn, white kernels are prized for a delicate, almost creamy sweetness milder than yellow sweet corn, pairing well with butter, cream, cheese, and herbs like cilantro, thyme, and basil.