Foot fungus is an infection that is most commonly found on the skin between the toes, and on the toe nails. When it spreads to the toe nails, the nails become thickened and distorted. The fungus is tinea pedis and it's actually a very small plant organism. Like all plants, foot fungus grows best in moist conditions. This is why many athletes get foot fungus. They sweat on their feet and their shoes don't breathe well enough. Once it starts growing, it is one of the hardest plants to kill and get rid of. Another good way to get it, is to walk barefoot on wet surfaces. Such as near a pool.