Voltmeter Measures voltage. The proper name for voltage is potential difference but voltage is more widely used.
Thermistor A transducer which converts temperature (heat) to resistance (an electrical property).
Resistor A resistor restricts the flow of charge. Uses include limiting the current passing through an LED, and slowly charging a capacitor in a timing circuit. Some publications use the old resistor symbol
Transistor NPN 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.