It's HC-06 Bluetooth module, Allows your device to both send or receive the TTL data via Bluetooth technology without connecting a serial cable to your computer.
Bluetooth version: V2.0+EDR; Works with any USB Bluetooth adapters. Built in antenna.
Default Baud Rate: 9600,8,1,n. Operating voltage: 3.3V.
Signal coverage: 30ft. Cable length: 21.5cm; Item size: 4.3 * 1.6 * 0.7cm; Item weight: 3g
Commercial Series: Bluetooth module board Series. With LED indicator light, use 150mA and 3.3V regulation chip. With VCC