Underwear is clothing worn next to the skin, designed primarily to cover, protect and provide comfort to the body. It is typically made of soft materials such as cotton, modal, nylon or synthetic blends. Underwear comes in a variety of styles and cuts, including undershirts, briefs, bras, briefs and boxer briefs, which can be selected based on gender and personal preference.

Thermal clothing is a special type of underwear designed to protect the body from the cold and retain heat. It is often made of technical materials such as polyester, polypropylene or merino wool, which provide effective insulation and transport moisture away from the body to ensure a comfortable and dry feel. Thermal clothing is particularly popular for outdoor activities in winter, such as skiing, snowboarding, hiking or mountaineering, but also in cold weather conditions in everyday life. It can be worn as a base layer under other layers of clothing to keep the body warm while allowing optimal freedom of movement.