Long underwear, also known as thermal underwear or base layer, is a type of clothing that you wear under your regular clothes to keep you warm. It's like wearing a cozy blanket on your body.
Long underwear is usually made of soft, stretchy fabric like cotton, wool, or synthetic materials. The fabric traps air between your skin and the outside environment to keep you warm. It also wicks sweat away from your skin, so you don't feel damp.
Long underwear typically covers your legs, waist, and sometimes your arms. It's important to wear it in cold weather or when you're doing outdoor activities like camping, hiking, or skiing.
Think of it like building a cozy house. You need a strong foundation to keep your house warm, and long underwear is like the foundation of your clothing. It helps keep your body warm so you can be comfortable outside in the cold.