Ohmmeter Measures resistance. Most multimeters have an ohmmeter setting.
Electricity is the flow of charge around a circuit carrying energy from the battery (or power supply) to components such as lamps and motors.
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.
Zener diode A zener diode can be used to maintain a fixed voltage.