Gamma rays are a form of light that we as human beings can not see with the naked eye. The composition of the rays is made up of electromagnetic radiation, EM raditation, with more than 10,000 times more energy than the visible light called photons. Since high radiation is produced from high-energy occurances, gamma rays are emitted by some of the most profound structures in the universe such as supernovas, a explosion of a massive star, neutron stars, which is the ending of a stars evolution wherein the star is supported by the neutrons, and black holes, stars that have evolved to the point that the gravity of the star can not be balanced by any other nuclear force.
Solar flares are now know to accelerate particles to very high energies thus producing gamma rays.
In our universe and throughout space there is light, whether it be visible light or infrared light. In the electromagnetic spectrum, gamma rays are the most intense forms of radiation. Well from earth, one can not see the distant explosion of a star. So scientists developed and constructed the GRO, Gamma Ray Observatory. By doing so, the study of the gamma ray universe, with the help of the GRO, will surely teach us of our own origins.