The Arduino Mega 2560 is a microcontroller board based on the ATmega2560. It has 54 digital input/output pins (of which 15 can be used as PWM outputs), 16 analog inputs, 4 UARTs (hardware serial ports), a 16 MHz crystal oscillator, a USB connection, a power jack, an ICSP header, and a reset button. It contains everything needed to support the microcontroller; simply connect it to a computer with a USB cable or power it with a AC-to-DC adapter or battery to get started. The Mega 2560 board is compatible with most shields designed for the Uno and the former boards Duemilanove or Diecimila.
Each Model of HC Bluetooth is very popular for using with any Microcontroller such as Arduino or STM. Bluetooth is easy for you to control wirelessly any device in short rang via your Phone or Computer. Bluetooth model of HC have communication protocol UART.
Module is used where short distance wireless communication is needed. The module is used for wireless communications of less than 100 meters. The module is preferred where power consumption is issue. HM-10 MODULE is designed by BLE chip so it consumes very less power to function. So the module can be used on mobile systems. The module uses UART communication and so it can be interfaced with almost all controllers or processors.