A thermos flask, also known as a vacuum flask, is a container designed to keep liquids hot or cold for extended periods. It consists of two walls with a vacuum in between, which minimizes heat transfer. This design helps maintain the temperature of beverages, making it popular for carrying coffee, tea, or soup. Thermos flasks are commonly made from stainless steel or glass and come in various sizes and styles. They are widely used for outdoor activities, travel, and daily commutes, providing convenience and ensuring that drinks remain at the desired temperature for hours.