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.
Voltmeter Measures voltage. The proper name for voltage is potential difference but voltage is more widely used.
A capacitor stores electric charge. Polarised capacitors must be connected the correct way round. They usually have larger values, 1µF and greater. See above for uses.
A NOT gate can only have one input. The o on the output means not. The output of a NOT gate is the inverse (opposite) of its input, so the output is true when the input is false. A NOT gate is also called an inverter.