A thermos is a container designed to keep liquids hot or cold for extended periods. It typically consists of two layers of glass or stainless steel, with a vacuum between them that minimizes heat transfer. This design helps maintain the temperature of beverages, making thermoses popular for carrying coffee, tea, or soup. Thermoses are often used for outdoor activities like camping or hiking, as they provide a convenient way to enjoy hot or cold drinks on the go. Many thermoses come with insulated lids and are available in various sizes, catering to different needs and preferences.