A skirt is a free-hanging part of an outer garment or undergarment extending from the waist down. Or long story made short, any piece of cloth that's hanging from your waist. :D While a dress is usually an outer garment (and usually for a woman/girl) consisting of a one-piece bodice and SKIRT. :D Hope this helped.

There is a big difference. This site has pictures http://www.athleta.com/products/womens-dresses-and-skirts.jsp