Insulators have valence shells that are more than half full of electrons and, as such, are tightly bound to the nucleus and difficult to move from one atom to another.

A schematic is the proper name for a drawing of an electric or electronic circuit.

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.

An amplifier is a device that takes a small input signal and creates a larger output signal. This makes it most similar to a step-up transformer which takes a smaller input voltage and creates a larger output voltage.

Electrons flow from an area of high concentration to an area of low concentration. A high voltage indicates a high concentration of electrons that creates a greater potential for electron flow than a low voltage. When applied to a load, voltage creates electricity and potential difference is the measure of voltage at a specific location in an electrical circuit.