While a Geiger counter merely determines count rates for radiation, gamma spectroscopy has the ability to determine both the count rate and the energy of the radiation. This turns out to be extremely important as different radioiosotopes emit many gammas of differing energies. A gamma spectrum is created by taking measurements of emitted gamma-rays and processing them. A detector could identify an unknown radioisotope by identifying features on the gamma spectrum and comparing them to known spectra.