The primary use of a thermos is to maintain the temperature of liquids, whether hot or cold. A thermos, or vacuum flask, consists of double-walled insulation, which minimizes heat transfer through conduction or convection. This design allows the thermos to keep beverages like coffee, tea, soups, or cold drinks such as iced tea and smoothies at desired temperatures for extended periods. Thermoses are widely used for their convenience in daily life, whether at work, during travel, or outdoor activities, helping consumers enjoy their favorite drinks without the need for immediate consumption.