A survey is given of the present state of theories concerned with the mechanism of supernova outbursts. Special attention is paid to the state of the star immediately before the supernova explosion (presupernova).
The following topics are discussed.
(1) The thermonuclear model of supernova explosions.
(2) The gravitational collapse model of supernova explosions.
(3) The characteristics of presupernova models resulting from the comparison of theoretical light curves with observational ones.