Conductors are those that can conduct electricity(They have some energy loss).
Insulators are those that block electric currect.
Semiconductor is somewhere between conductor and insulator.
Superconductors shows zero resistance. So you can run current through and you won’t lose any energy.
Superconductors are normally conductors.
They become superconductor in only certain situation.
Standard Definition :
Applications of SuperConductors :
Magnetic-levitation is an application where superconductors perform extremely well. Transport vehicles such as trains can be made to "float" on strong superconducting magnets, virtually eliminating friction between the train and its tracks.
Electric generators made with superconducting wire are far more efficient than conventional generators wound with copper wire. In fact, their efficiency is above 99% and their size about half that of conventional generators.
An area where superconductors can perform a life-saving function is in the field of biomagnetism. Doctors need a non-invasive means of determining what's going on inside the human body. By impinging a strong superconductor-derived magnetic field into the body, hydrogen atoms that exist in the body's water and fat molecules are forced to accept energy from the magnetic field. They then release this energy at a frequency that can be detected and displayed graphically by a computer. Magnetic Resonance Imaging (MRI) was actually discovered in the mid 1940's.
But, the first MRI exam on a human being was not performed until July 3, 1977. And, it took almost five hours to produce one image!
Reference : http://www.superconductors.org/