Kneading gloves are for kneading dough with.
They have two purposes. They let you knead dough, without it sticking to your hands, and they help to diminish the flow of heat from your hands to the dough, which can make the dough stickier. Without the dough getting stickier, you also need less flour to help prevent the dough sticking.
They are made of nylon and come in a pair (e.g. 2 per set.) One size fits all. They work for both right and left-handed people (sic.)
To use, put the gloves on, rub flour into them, then shake excess flour off, and proceed with your kneading.
Most call for hand-washing afterwards.