HC-05 is a class-2 Bluetooth module with Serial Port Profile, which can configure as either Master or slave. a Drop-in replacement for wired serial connections, transparent usage. You can use it simply for a serial port replacement to establish a connection between MCU, PC to your embedded project and etc.
To setup Wireless Serial Communication, HC-05 Bluetooth Module is most demanding and popular due to its low price and extremely high features. This module can be used in Master or Slave Mode and easy switchable between these two modes, By default Slave mode is configured. Modes can be changed using AT Commands.