All electricity is the movement of electrons which are subatomic particles that orbit the nucleus of an atom. Electrons occupy various energy levels called shells and how well an element enables the flow of electrons depends on how many electrons occupy its outer (valence) electron shell.

Resistors are used to limit voltage and/or current in a circuit and can have a fixed or variable resistance.  Variable resistors (often called potentiometers or rheostats) are used when dynamic control over the voltage/current in a circuit is needed, for example, in a light dimmer or volume control.

A fuse is a type of low resistance resistor that stops current flow in a circuit in response to a larger than intended electric current flow. Using a fuse with a higher current rating than required by a circuit is less safe as it could potentially allow overcurrent and risk a fire or heat-related equipment damage.

Capacitors store electricity and are used in circuits as temporary batteries. Capacitors are charged by DC current (AC current passes through a capacitor) and that stored charge can later be dissipated into the circuit as needed. Capacitors are often used to maintain power within a system when it is disconnected from its primary power source or to smooth out or filter voltage within a circuit.

In the NM cable used for wiring homes, each cable has three wires inside a sheath with each wire covered in a different color of insulation to indicate its type. The wire with the black insulation is the 'hot' wire, white is the neutral wire, and the ground wire is either covered in green insulation or left bare.