Supernovae are exploding stars, the very final stages of evolution for some stars, that release tremendous energy. All supernovae are produced via one of two different explosion mechanisms i.e. the core-collapse of massive star and the thermonuclear explosion of a white dwarf which has been accreting matter from a companion. Supernovae of Type Ia, deprived of hydrogen and rich in heavy elements, play important roles in diverse areas of astrophysics from the chemical evolution of galaxies to observational astronomy. These are the thermonuclear explosions of white dwarfs accreting mass to reach the Chandrasekhar limit, they have homogeneous properties and are used as standardized candles. Photometry is the most easily acquired information about supernovae. The light curves constructed from regular imaging provide signatures not only for the energy input, the radiation escape, the local environment and the progenitor stars, but also for the intervening dust. They are the main tool for the use of the supernovae as distance indicators through the determination of the luminosity. The construction of bolometric light curves provides the most direct link to theoretical predictions. And an analysis of their spectra yields insights into the explosion mechanism.