Not quite the same thing. It's rather like the difference between what and which (which are the generally accepted translations of the related words kio and kiu).
Tio = that (thing) (affair, object), it. De kie tio venis? Where did that come from?
Tiu = that one (person, thing), the one (he, she, it) over there. Tiu pilko venis el la kampo. That ball came from the field.
Tio is used when one doesn't have a specific something about which one is speaking. If there is a specific person, place or thing then one would use tiu. Or, another way to see it, Tiu references the noun, tio replaces it.
Hopefully that (tiu) helps. It really is both that (tia) simple and that (tia) complex.