Skirts and dresses: one might think they would be completely non-interchangable as garments. After all, you don't see people walking around with their arms stuffed through the legs of shorts, or wearing socks stretched over their heads. But, somehow in the past two years or so, people started hitching up skirts over their boobs, and, at times, belting them for "definition." (Random belting is a dire problem itself that will be attended to in time.)
The problem therein, is that dresses are made to fit breasts, hips, and waists, and the a-line skirts people are forcing into dresses are just made to fit waists, and usually just flow over one's hips. Therefore, making them into so-called "dresses" creates a triangular or lampshade-like appearance. (As seen at bottom right)
Adding a belt, as shown in the photo at left, just makes the areas not constricted by the belt pouf out. In case you've been wondering, it doesn't hide the fact that you're wearing a skirt and not a dress. It simply highlights the fact that you've added a belt to the skirt you're wearing under your armpits for some reason.
And if you're wondering just what to do with that long, patterned a-line skirt, here's some advice: throw it away. Those types of skirts are ugly to begin with.