Spectral Aspects of the Evolution of Gamma-Ray Bursts

A review on the spectral and temporal properties of gamma-ray bursts is given. Special attention is paid to the spectral evolution of their continuum emission and its connection to the time evolution of the intensity. Efforts on systematizing these observations as well as the effects due the limitations of the current detectors on the observed sample are discussed. Finally, physical models that aim at explaining the observations, are addressed.