Stars that have mass greater than about 1.5 times that of our sun, end their lives with much fanfare.
The carbon-oxygen core formed at the red giant phase has so much mass that gravity shrinks the core further, causing its temperature to become very high.
At these high temperatures, nuclear reactions fuse carbon and oxygen to successively heavier elements like neon, silicon, and finally, iron. In the layers outside the iron core, nuclear reactions continue.
The enormous energy released in these reactions causes the outer layers (minus the iron core) to explode like a massive bomb.
This marks the death of the star. Such an exploding star is called a supernova.