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.