Conductor, Insulator and Semiconductor

Let us have two metallic balls. One of them is strongly charged and the other one is electrically neutral. If we now join them with iron wire or by metallic substance, then the neutral metallic ball will gain charge. Now if we touch them all with a wooden stick or rubber, then the neutral ball still remains neutral or chargeless. So, a substance like iron or metallic balls are called electrical conductors and wooden stick or rubbers is called nonconductor or insulator. All metals are well electrical conductors.

Silicon and Carbons are called semiconductors. Semiconductors are in the middle category in sense of conductors and insulators.