Gamma Rays were found to be very short wave radiation, more penetrating and of shorter wavelength than even X-Rays. The table below describes the different radiations of the Electromagnetic Spectrum. I must emphasise that these radiations are all the same except for the difference in wavelength. They have different names because of historical reasons and the way they are generated. The boundaries between the different radiations are all artificial.
All matter produces radiation.
Radio Waves are produced when free electrons are forced to move in a magnetic field, or when electrons change their spin in a molecule. They are used for communication and to study low energy motions in atoms. All electrical goods generate Radio Waves. Radio Waves from space can be used to study cool interstellar gases. Radio Waves cannot be detected by humans.