Corns are hard, painful lumps on the skin. They typically develop on the tops and sides of your toes.
Corns are caused by constant rubbing and pressure from shoes that are too tight.
Make sure you're not wearing shoes that are not long enough or too narrow. You should have plenty of room in the toebox. If you can't wiggle your toes, your shoes are too tight. If you already have a corn, use a layer of Vaseline over it to prevent more corns from forming.
After you make sure you're wearing shoes that fit properly, take some of the pressure off the corn by putting a corn cushion on it. Corn cushions, which are sold at most drugstores, are small pads with a hole in them that reduces friction when fitted over the corn. You can also rub the corn with a pumice stone or emory board after bathing to help remove the layer of toughened skin. If the corn is very painful, you may need to have it professionally removed with a scalpel.