• HC-05 is a powerful classic Bluetooth module. It is based on the Bluetooth 2.0 standard and supports multiple transmission protocols, including serial communication (UART) and Bluetooth SPP (serial communication). It can transmit data and communicate with other devices through these protocols. Commonly used for wireless communication with microcontrollers (such as Arduino).
  HC-05 can switch between master mode (Master) or slave mode (Slave) and supports Bluetooth SPP (serial communication) and AT command mode. Has high flexibility.
  It supports the setting of Bluetooth connection passwords to improve security.
• HC-06: The HC-06 module only supports Bluetooth SPP (serial communication) protocol. It does not have UART transmission protocol support, so when using HC-06 to communicate with other devices, data needs to be transmitted through the serial port.
  HC-06: The HC-06 module is mainly used in slave mode (Slave). It cannot switch to master mode and can only accept connection requests from the master device.

HC-05/HC-06 can be configured and controlled through AT commands, such as changing the Bluetooth name, baud rate, pairing password, etc. They have a basic communication range, usually around 10 meters.