The document introduces semiconductor materials, defining them as materials that can be conditioned to allow or suppress electrical current flow. It discusses the atomic structure of semiconductors like silicon and how doping them with impurities makes them conductive. Doping can produce either an excess of electrons, making it an N-type semiconductor, or a shortage of electrons resulting in holes, making it a P-type semiconductor. The conductivity and resistance of the semiconductor depends on the amount of doping.