"That is the end."
Translation:Tio estas la fino.
As johmue is explaining:
That is good = Tio estas bona
That thing is good = Tiu afero estas bona
See how tiu and afero stands together as opposed to the uppermost sentence?
It's possible to imagine a context where "Tiu estas la fino" might be possible, but generally, "Tio..." is much more likely.
Use "tiu" when you're making a choice between two or more alternatives, i.e. when you're indicating "which one". If there's a stack of books and someone asks, "Which one's yours?", you can answer "That one!" = "Tiu!"
But here, it's difficult to imagine how it could mean "That one there, that is the end". That... what, exactly?
Hope that helps.
Because "tiu" cannot stand alone. It has to stand with some (maybe implicit) noun.
Okay, reading all of this it now makes more sense. I've long been confused by the difference.
It sounds like 'tio' is a demonstrative pronoun while 'tiu' is a demonstrative adjective. Is that correct?