Frogs get water by obsorbing it through their skin. Frogs also get oxegen through their skin, along with their lungs, meaning that frogs can suffocate if they don't take care of it.
Some frogs have a mucus on their skin that helps keep it moist, but they still need to stay near water.
The skin of a toad is rougher than the skin of a frog, and it dosn't dry out as quickly.
Frogs need to keep their skin healthy, so they shed it. The frog will start to twist, turn and act like it has the hiccups. The reason they do this is so that they can stretch out of their old skin. Frogs shed their skin at different intervals. Some do every week, some every day! The frog then pulls the skin over it's head, and after it's done, it eats it.