The "three-layer system" refers not to three separate garments, but to three functional layers: a moisture-managing base layer, an insulating mid-layer, and a protective outer shell. By combining garments that serve these functions, you create a versatile system. You can adjust each layer based on environment and activity level to achieve critical goals: blocking wind and precipitation (windchill & wetness), while effectively moving sweat away from your skin (avoiding conductive heat loss). This dynamic balance prevents both overheating and excessive cooling, maintaining an optimal microclimate.