A skirt covers area from the waist down. A dress covers top/bottom - Usually a one piece item. Mini skirts are skirts - just SHORTER versions. but yes, they are considered skirts. Otherwise, they'd be shorts. Evening gowns are real dresses.. but they are FORMAL dresses... usually to your ankle. Anything shorter than that that is "formal" could be considered a cocktail dress - usually basic black is the most popular. Those are the definitions to me ~ why? Don't know if there is a WHY... but most girls know the difference before too long. Hugz.
A skirt is a "bottom" that does not have individual holes for each leg. A dress is a one-piece (top and bottom) that doesn't have individual holes for each legs. Yes, a mini skirt is really a skirt and an evening gown is really a dress, they're just specific types of skirts and dresses.
a skirt is a single peice of fabric that wraps around both legs, a dress is the same thing really but it covers up the torso as well, evening gows are long, formal dresses, like prom or wedding gowns, or red carpet gown.