The end of the world is… when you die, this is the end of your life in this world and you will never return to the planet Earth with a body. Your soul will travel, transform, or whatever happens to God to see the result of rightful things you did to others.
Everything in the universe had a start, and will have an end, this would be in millions of years, or any day if we destroy it with our great weapons or bad choices. But you shouldn’t worry about the end of the world per se, it is more likely that you will just die like every other human being in the history of mankind, that is, NOT because of an end of the world catastrophe, but of desease, injury, sickness, parasite, etc.
Enjoy your days, each day will never happen again, thank God for his creation, smile more, stop worrying, that WILL kill you.