Neutrinos from a supernova arrive before the light due to their ability to escape the star's dense outer layers almost immediately, while light takes longer due to interactions with ions and electrons. The process begins with the neutronization phase, where neutrinos are released right away, whereas photons are delayed as they travel through the star. This phenomenon highlights that over 99% of a core-collapse supernova's energy is emitted as neutrinos rather than light. The shock wave from the supernova can take hours to become visible, further contributing to this timing difference. Understanding this sequence is crucial for astrophysical studies of supernovae.