Together action is like washing potatoes. When people wash potatoes in Korea, instead of washing them one a time, they put them all in a tub full of water. Then someone puts a stick in the tub and pushes it up and down, up and down. This makes the potatoes rub against each other. As they bump into each other, the hard crusty dirt falls off. If you wash potatoes on a time, it takes a long time to clean each one, and only one potatoes gets clean at a time. If they're all together, the potatoes clean each other.