3-finger (or lobster) gloves are the middle-ground option when you need more warmth than gloves provide but still want functional dexterity. Your index finger stays separated for grip and fine tasks, while your other three fingers share a compartment to pool body heat—much like a mitten.
They shine in cold conditions where regular gloves leave your hands freezing but full mittens feel too clumsy. Backcountry skiers love them because you can still operate bindings, adjust goggles, and grip poles without freezing. Resort skiers with chronically cold hands also benefit on bitter days.
The trade-off is that they're not quite as warm as full mittens, and you lose some dexterity compared to gloves—try zipping a jacket with three fingers grouped together. But for most cold-weather skiing where pole grip matters, they hit a sweet spot that gloves and mittens can't match.