The word "conductivity" is used to describe a material's ability to transport electricity. This ability varies in different materials. Metals, like copper and gold, are good conductors. Glass or plastics, on the other hand, are very bad conductors. In fact, they don't conduct at all. Materials that don't conduct current are called insulators. Semiconductors, like silicon, are materials with conductivity somewhere between good conductors and insulators.

Why are semiconductors so special? For one thing, we can very easily control how current passes through them. We don't have that option with metal since metal conducts electricity under almost any condition. Because of this, semiconductors are ideal for the construction of electric components such as transistors. Transistors can serve as switches (on/off) or amplifiers, and are the key elements in integrated circuits. Integrated circuits are more commonly known as microprocessors, computer chips or memory chips, and consist of millions of transistors packed onto a tiny piece of silicon.