  The physics of radio emission from cosmic-ray induced air showers is shortly
summarized. It will be shown that the radio signal at different distances from
the shower axis provides complementary information on the longitudinal shower
evolution, in particular the early part, and on the distribution of the
electrons in the shower core. This complements the information obtained from
surface, fluorescence, and muon detectors and is very useful in getting a
comprehensive picture of an air shower.
