There's a bit of confusion around this since they are both course-ground cornmeal. The primary differences lie in the type of corn used to make it and the processing of the corn. Polenta is made with flint corn, whereas grits are made with dent corn. Since dent corn contains more starch than flint corn, grits have a more gummy texture than polenta. Grits are made from ground hominy, which is commonly white corn that's been treated with a lye solution. This process changes the flavor, texture, and nutritional profile of the corn. Polenta is made from untreated yellow corn.