Hello everybody, this is my first official tutorial on Instructable.com, I’m very excited about my first project!
Today I will show you How to connect Arduino and Bluetooth module. Arduino will communicate with the HC-06 Bluetooth Module Board using Serial communication. (this tutorial also works no HC-05)
WATCH INTRO HERE
The Bluetooth module we will use today is HC-06 which is well-known and cheap. (I got mine for 2$ from aliexpress)
What is HC-06?
The HC-06 is a class 2 slave Bluetooth module designed for transparent wireless serial communication. Once it’s paired to a master Bluetooth device such as PC, smartphones or tablet, its operation becomes transparent to the user. All data received through the serial input is immediately transmitted over the air. When the module receives wireless data, it is sent out through the serial interface exactly at where it is received. No user code specific to the Bluetooth module is needed at all in the user microcontroller program.
We will also use Serial communication for today’s project. For Arduino, it is by default RX and TX pins (D0, D1)
For more information visit: https://www.arduino.cc/reference/en/language/functions/communication/serial/
After reading this instructable you will be able to:
1) Connect Arduino Board with any Android phone by Bluetooth and send/receive data.
2) Build a project and read values from sensors wirelessly
3) Build a Home Automation or wirelessly controlled robot.”

Link