The HC-05 or HC-06 Bluetooth Module (Master/Slave) provides a wireless communication link between your Arduino and any bluetooth capable device. It’s ideal replacement to your wired serial connection. It enables a circuit to communicate to another circuit through wireless connectivity. Sending and Receiving of data can be achieved within a range of 10 meters. Has a standard 2-pin UART connection (Tx & Rx) which makes it very easy to connect to your microcontroller board like the Arduino.
The module board has signal conditioning circuit (5V and 3.3V compatible) to easily connect the signal pins directly to Arduino boards or any 5V powered device. No need for a (3.3v signal line) voltage divider or voltage switching circuitry.