  Core-collapse supernovae are among the most energetic explosions in the
universe marking the catastrophic end of massive stars. In spite of rigorous
studies for several decades, we still don't understand the explosion mechanism
completely. Since they are related to many astrophysical phenomena such as
nucleosynthesis, gamma-ray bursts and acceleration of cosmic rays,
understanding of their physics has been of wide interest to the astrophysical
community.
  In this article, we review recent progress in the study of core-collapse
supernovae focusing on the explosion mechanism, supernova neutrinos, and the
gravitational waves. As for the explosion mechanism, we present a review paying
particular attention to the roles of multidimensional aspects, such as
convection, rotation, and magnetic fields, on the neutrino heating mechanism.
Next, we discuss supernova neutrinos, which is a powerful tool to probe not
only deep inside of the supernovae but also intrinsic properties of neutrinos.
For this purpose, it is necessary to understand neutrino oscillation which has
been established recently by a lot of experiments. Gravitational astronomy is
now also becoming reality.
  We present an extensive review on the physical foundations and the emission
mechanism of gravitational waves in detail, and discuss the possibility of
their detections.
