GATT is a protocol used in Bluetooth Low Energy (BLE) for communication between devices. It defines how data is transferred between a client (like a smartphone) and a server (such as a wearable device). GATT specifies services and characteristics for managing various device functionalities like heart rate monitoring or step counting. It is widely used in IoT devices, health trackers, and other wireless peripherals. With GATT, developers can easily design applications that interact with BLE-enabled hardware through well-defined profiles.