Well, here are some answers to your questions. Nordic skiing or is a style of skiing done on more gentle terrain like a tour around a meadow or over a small ridge. Touring skis feature the classic technique of gliding from one leg to the next in a straight line. The arm opposite the pushing, or kicking, leg pushes off the ski pole for added propulsion. Touring skis come in different lengths.
Flotation is how stable the skis are in deep snow.
Short skis can be used on groomed trails but they also can be used on terrain that has not been groomed or packed. Narrower skis are designed for performance and speed and provide less flotation. They are designed for groomed trails and packed surfaces. Long skis are generally faster on soft snow. The longer ski produces an easier and faster glide and spreads the load out so there is less friction between the ski and the snow's surface.