Unlike pants, which fully cover each of your legs separately, a skirt is basically a single piece of fabric covering part of your legs. If you want to show a little leg, wear a skirt!
Skirts can be very short (like a miniskirt) or so long they drag on the ground. Long ago, skirt was also rude slang for a young woman. As a verb, skirt means "go around," like when you skirt a city instead of driving straight through it. The word outskirts, "outer parts or fringes" is related.