An AC adapter is a device that converts alternating current (AC) from a wall outlet into direct current (DC) to power electronic devices. It typically consists of a transformer and a rectifier, allowing it to supply the correct voltage and current needed for devices like laptops, smartphones, and tablets. These adapters are essential for charging batteries and providing power to devices that do not have built-in power supplies. They come in various shapes and sizes, often with interchangeable plugs to fit different devices, ensuring compatibility with products from brands like Apple, Samsung, and Dell.