Materials are classified as conductors, insulators, or semiconductors according to their electric conductivity.
The semiconductor is composed of two words-Semi and Conductor. Semi means not completely while conductor mean something, which can conduct electricity. Everybody is familiar with "Electricity". It is present everywhere; it runs many appliances in your home and outside the home like TV, Bulb, Freeze, and Microwave Oven etc.
So a conductor is nothing but a material having ability to conduct this electricity. Semiconductors conduct electricity to some extent, less than the conductors.
A semiconductor is a material that has intermediate conductivity between a conductor and an insulator. It means that it has unique physical properties somewhere in between a conductor like aluminum and an insulator like glass. In a process called doping, small amounts of impurities are added to pure semiconductors causing large changes in the conductivity of the material. Examples include silicon, the basic material used in the integrated circuit, and germanium, the semiconductor used for the first transistors.