The supernova rate: a critical ingredient and an important tool
  In this review I summarize the role of supernova rate as a critical
ingredient of modern astrophysics, and as an important tool to understand SN
explosions. Many years of active observations and theoretical modeling have
produced several important results. In particular, linking SN rates with parent
stellar populations has proved to be an important strategy. Despite these
advances, the situation is far from clear, in particular for the SNe Ia.
