Zener diode A zener diode can be used to maintain a fixed voltage.
Phototransistor A light-sensitive transistor.
LDR A transducer which converts brightness (light) to resistance (an electrical property). LDR = Light Dependent Resistor
Transistor PNP A transistor amplifies current and can be used with other components to make an amplifier or switching circuit. This symbol is for a bipolar junction transistor (BJT), the type you are most likely to use at first.