SoftwareSerial HC06 , Android Bluetooth Terminal to Control Arduino

 SoftwareSerial  HC06

https://www.youtube.com/watch?v=2eM6dhwcLPc

https://www.youtube.com/watch?v=x3KAXjnP06o

https://www.instructables.com/Tutorial-Using-HC06-Bluetooth-to-Serial-Wireless-U-1/