Resistors can be chosen in a wide variety of values to control the voltage in a circuit, limit the current, or moderate the heat produced by the components in the circuit.

A transistor works by allowing a small amount of current applied at the base to control general current flow from collector to emitter through the transistor. A transistor acts as a gate or switch for electronic signals.

All conductors have resistance and the amount of resistance varies with the element.  But, resistance isn't the only consideration when choosing a conductor as the most highly conductive elements like silver and gold are also more expensive and more brittle than slightly less conductive elements like copper. A balance needs to be struck between the electrical qualities of a material and its cost and durability.

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

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.