General Caption: Stellar evolution has 2 main paths depending on stellar mass:

1. Stars less massive than ∼ 8 M_☉ end their lives as white dwarfs; those more massive that ∼ 8 M_☉ end their lives by exploding as supernovae.
2. Thus, 8 M_☉ is a usual main dividing line between low and high-mass stars.

Images:

1. Image 1 Caption: A cartoon of the evolution of the Sun or a Sun-like star. Also, mutatis mutandis, any star in the stellar mass range ∼ 1--8 M_☉.

   

2. Image 2 Caption: A cartoon of the evolution of a high-mass star: i.e., star in stellar mass range ∼ 8--40 M_☉ (Wikipedia: Stellar Evolution: Massive stars). Stars more massive than ∼ 40 M_☉ also explode as supernovae, but their stellar evolution is a bit different than those stars in the stellar mass range ∼ 8--40 M_☉.

   Note iron (Fe, Z=26) undergoes endothermic nuclear burning NOT exothermic nuclear burning. So trying to burn iron cools the iron core. At this point, electrons in the iron core find it energetically favorable to very rapidly bind with the protons (of the iron nuclei) via electron capture (p+e(-)→n+μ_e) to create neutrons. The rapid disappearance of the electrons and their degenerate electron gas pressure leads to an implosion. The implosion turns into an explosion because the creation of the neutrons releases neutrinos (specifically electron neutrinos which in this dense environment do interact significantly with matter) which push outward the outer layers of the star. The explosion is a, in fact, core collapse supernova.

Images:

1. Credit/Permission: © David Jeffery, 2003 / Own work.
   Image link: Itself.
   
2. Credit/Permission: © David Jeffery, 2005 / Own work.
   Image link: Itself.