The characteristics of mittens, lobster and cross-country gloves
In cross-country skiing there are 3 types of gloves: mittens, "lobsters" and gloves. Mittens are the warmest of the three because they have only two compartments allowing the fingers (from the index to the little finger) to keep their heat. It is therefore more suitable for skiers who tend to have very cold fingers. Swix Lahti mittens are a good example.
The lobsters, or 3 finger gloves, have 3 compartments to provide a better grip than the mitten and to keep your hands warmer than wearing gloves. Gloves, on the other hand, make it easier to handle objects. Some gloves are very thin, like Bjorn Daehlie's Speed Synthetic and others are thicker like the Sportful Engadin Warm. Gloves, however, are the alternative that keeps the warmest.
Our cross-country ski gloves have a thumb with polar as a tissue. In addition, on the back of the hand, most of our gloves / mittens / lobster are equipped with a membrane that cuts the wind. On colder days, you can add a layer by putting on a thin, thin glove like the Wigwam Poly liner under your mitten / lobster / glove.