  There is mounting evidence that long duration gamma ray bursts (GRBs) and
X-ray flashes (XRFs) are produced by highly relativistic and narrowly
collimated jets ejected in core collapse supernova (SN) explosions akin to SN
1998bw. We review the history of the GRB-SN association idea and its
observational verification. We summarize the present evidence for a GRB/XRF-SN
association. We comment on the possibility that most, perhaps all, SN
explosions produce GRBs, including SNe of Type Ia which may produce short
GRBs/XRFs. We list the major open questions that follow from a GRB/XRF-SN
association. Possible uses of the GRB-SN association in cosmology are pointed
out.
