A rice cooker is a small kitchen appliance designed to automatically cook rice by keeping it warm and moist while it simmers. It typically has a built-in thermostat that regulates heat, allowing the user to simply add rice and water, set the desired level of doneness, and press start for the machine to do all the work. Rice cookers come in various sizes and styles, with some featuring additional functions such as steaming or even making congee (a type of rice porridge).