The ATMega328 board is a microcontroller board based on the ATmega328, The board contains everything needed to support the microcontroller. The board need 5VDC to power it. Simply connect the power connector to a computer with a USB cable or power it with a AC-to-DC adapter or battery to get started. You can program it with the ICSP connection. The ATMega microcontroller boards can be programmed with a serial port programmer, parallel port programmer or USB port programmer.
- 20 digital input/output pins (of which 6 can be used as PWM outputs and 6 as analog inputs)
- 16 MHz crystal oscillator,
- RS232 connection for communication with your PC,
- power jack,
- ICSP header,
- reset button.
for more detail: ATMega328 Board