The ATMega328 board is a microcontroller board based on the ATmega328. It has 14 digital input/output pins (of which 6 can be used as PWM outputs), 6 analog inputs, a 16 MHz crystal oscillator, a RS232 connection, a power jack, an ICSP header, and a reset button.
A photocell or photo resistor is a Light Dependent Resistors (LDR). LDR's are sensors that detect light. They are small, inexpensive, low-power, easy to use and don't wear out.
This LCD message display can show text with large characters on an 20*4 LCD module. The display can show five characters at a time. Each characters is build from twelve characters of the display module. The text on the display can be read from up to ten meters distance.