For another device like a smartphone to use any of the Bluetooth “services” which the board has, it must first be paired with the board. Once paired, the other device may connect to the board and exchange data relating to many of the board’s features.
This block starts an event handler which in this case will run when something connects to your board using Bluetooth.
bluetooth.onBluetoothConnected(() => {});You could use this event handler to display a letter “C” on the board LED grid so you know you have a Bluetooth connection. Or you might want to send some data you’ve been accumulating to your smartphone as soon as it connects to your board. Maybe you’ve been using the accelerometer in your board to count your steps for example. Using this event handler you could send the accumulated step count to your phone when it establishes a Bluetooth connection.
bluetooth.onBluetoothConnected(() => {
basic.showString("C");
});About Bluetooth, board Bluetooth profile overview , board Bluetooth profile reference, Bluetooth on board resources, Bluetooth SIG
bluetooth