Conductors are materials that have low resistance. The low value allows them to easily pass through an electrical current because of the very free electrons. Most metals are good conductors of electricity because they also have low resistance. Metals such as copper and metal are good conductors of electricity they still have some resistance to the flow of electrons.
What are they used for?
Semiconductors are materials which have conductivity between conductors, generally metals, non conductors, and insulators. Semiconductors can be pure elements. Examples are: Germanium, silicon, selenium, cotton, and wool.