Peltier modules, also known as thermoelectric coolers, are devices that create a temperature difference when an electric current passes through them. They consist of two different types of semiconductor materials, which are arranged in a series of junctions. When electricity flows through these junctions, one side absorbs heat and cools down, while the other side releases heat and warms up. These modules are commonly used in various applications, such as refrigeration, temperature control, and electronic cooling. They are compact, lightweight, and can be easily integrated into systems, making them a popular choice for cooling small devices like CPUs and lasers.