Cornmeal

Cornmeal is simply ground dried corn and is often fairly coarse in consistency, and usually yellow in color, though you can find white cornmeal too.

Coarse cornmeal and medium-ground cornmeal can be used for making polenta (traditional corn polenta is essentially the same thing, except it’s made from flint corn instead of dent corn; still, either kind can be cooked into a thick porridge). This coarser cornmeal is also handy for ensuring a pizza crust doesn’t stick to a skillet or baking sheet

More finely ground cornmeal can be used to dredge food for frying, and while the consistency used can vary by recipe, cornmeal is also the primary ingredient in cornbread and many other baked goods.

If you like to DIY, you can make your own cornmeal by grinding popcorn kernels in a food processor or high-powered blender. For the best corn flavor, though, look for stone-ground cornmeal—but note that it doesn’t last quite as long since the oily germ and bran are not removed before grinding and they are more perishable.

Grits are technically just another form of cornmeal, but are even more coarsely ground, and are also sometimes made from hominy, which is corn that has been treated with lime to remove the hull and germ.

Masa

Masa harina is also made from hominy, but is ground much finer (usually to the same consistency as all-purpose flour—masa is sometimes called corn flour, in fact). While generally white in color, you can find yellow masa too, and even blue masa harina (labeled azul).

All masa is treated with slaked lime or wood-ash lye and is made from a wet corn dough that is then dehydrated so it can be stored longer (that is, the dried corn kernels are cooked and soaked in lime water, then ground while wet before being dried out into the fine flour).

To make masa dough, all you have to do is add water back. Masa is the main ingredient in homemade corn tortillas and in tamales. You can also add small amounts of masa to things like chili and soups as a thickening agent, and use it in place of wheat flour in many recipes too (including cornbread).