They’re basically inside-out rabbit/possum skins that go over your handlebars and let you slip your hand through a hole into a furry ball of warmth. You can access your brakes/gears which are also inside the fur. The best ones are waterproof too.

Downsides, signalling becomes a little bit more work in that you have to pull your hand from the pog first. Likewise, if you’re falling over then your hand is somewhat encumbered. Still beats frozen fingers IMO.