Bluetooth uses radio waves for broadcasting and communication between devices. Specifically, Bluetooth uses short-range radio waves in the 2.4 GHz frequency band to establish a wireless connection between devices.
When a Bluetooth-enabled device is in discoverable mode, it broadcasts a radio signal, known as a Bluetooth signal or beacon, that can be detected by other Bluetooth devices within range. This signal contains information such as the device's name, unique identifier, and other details that allow other devices to identify and connect to it.