The HC-06 is a slave Bluetooth 2.0+EDR serial (UART) pass-through module. It can easily pair with a master Bluetooth device, but cannot pair with another slave device.
It can be connected to the serial pins on your Arduino or other dev board and serve as a wireless serial link, all without having to do anything except connect power, ground, Tx, and Rx. Once powered, the module automatically starts broadcasting its ID waiting for a master Bluetooth device to pair with it.
The module has an on-board voltage regulator which allows you to power the module with supply voltages of 3.6V to 6V.
With a logic level of 3.3V you can directly connect this module to a Raspberry Pi but we recommend using a logic level converter when connecting it to 5V logic devices such as most Arduino boards.