The End of the World

What exactly does that phrase mean, the “end of the world?”

I was listening to a song that had it as a catchy lick at the end repeated at a cadence in syncopated repetition with the implication that something (a giant meteor, nuclear war maybe) was about to wipe out everything. 

But, out of that context, what exactly does the end of the world mean? 

Is it a literal end to everything living or a metaphorical end as in all the things familiar are changing?

I usually take it to be the latter, which is slow dissolution of the familiar to be replaced by the new. Not pleasant, but definitely not the end. 

Just something different. Not the end of the world as we know it. More like the change of the world as we know it.

Still scary, but WAY different than the end.