  The location accuracy of the BeppoSAX Wide Field Cameras and acute
ground-based followup have led to the detection of a decaying afterglow in X
rays and optical light following the classical gamma-ray burst GRB 970228. The
afterglow in X rays and optical light fades as a power law at all wavelengths.
This behaviour was predicted for a relativistic blast wave that radiates its
energy when it decelerates by ploughing into the surrounding medium. Because
the afterglow has continued with unchanged behaviour for more than a month, its
total energy must be of order 10**51 erg, placing it firmly at a redshift of
order 1. Further tests of the model are discussed, some of which can be done
with available data, and implications for future observing strategies are
pointed out. We discuss how the afterglow can provide a probe for the nature of
the burst sources.
