What are Base Layers?
Popularly known as Base layers, these items of clothing also go by Thermal wears or colloquially known in Singapore as Long Johns as well.
Regardless of it's name, Base layers are one part of the 3 layering method. Your inner-most layer, Base layers are meant to keep you dry as you perspire (YES you still perspire in the cold!) and thus help to regulate your body temperature.
This will prevent you from getting cold when perspiration from your skin transfers into the fabric. This property of the Base layer is called moisture wicking. In essence, a good Base layer keeps you dry, comfy and warm.