A NOR gate can have two or more inputs. The o on the output means not showing that it is a Not OR gate. The output of a NOR gate is true when none of its inputs are true.
Preset variable resistor A preset is operated with a small screwdriver or similar tool. It is designed to be set when the circuit is made and then left without further adjustment. Presets are cheaper than standard variable resistors so they are sometimes used in projects to reduce the cost.
Microphone A transducer which converts sound to electrical energy.
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.