Clusters of galaxies are the largest virialized systems in the universe and represent astrophysical laboratories for studying a wide variety of phenomena. These range from the properties of individual galaxies, to those of the intracluster medium, and to the violent events that accompany cluster mergers. In this talk I will concentrate on the non thermal components of galaxy clusters, i.e. those detected from synchrotron emission in the radio band. The radio emission provides information on large scale magnetic fields and on relativistic particles. This is needed, in addition to the optical and X-ray information, to draw a comprehensive picture on the physical conditions of clusters of galaxies.