stars are giant burning balls of gas which can emit light (that’s why there bright against the night) some of the stars you see in our night sky have already exploded but they are so far away that the light from the explosion still reaches us even though they can have exploded 100 years ago!
Someday, the a star Betelgeuse will run out of fuel/energy, collapse under its own weight, and then turn into an amazing supernova explosion! this could actually happen in just under a year hence another reason to say that the world will end 😦
Zak Science 
oh no not the world ending :O