A poncho is a garment made in one piece with a hole in the middle to put it over your head. Ponchos originally come from Peru. They can be made out of virtually anything, but are often made from wool to keep the person wearing them nice and warm.
A raincoat is a piece of clothing made from waterproof fabric. Raincoats are designed to keep you dry when you are outside in the rain.
A skirt is piece of clothing that has a band around your waist but otherwise is just cloth below the band. Skirts go around both of your legs and not between them.
Skirts come in all lengths from very short, knee length like the one in the picture, or even down to your ankles. Usually only women and girls wear skirts.