Resumé or CV?

Is there any difference between the term 'resumé' and 'curriculum vitae'?
Yes

Why are they used interchangeably in Australia?
Often these terms are used as if they mean the same thing. They do have individual meaning.

What are the differences?
Resumé = summary.

Curriculum Vitae = fuller, more descriptive summary. Generally for positions with higher levels of responsibility.

Portfolio = resumé or curriculum vitae with artifacts such as reports or examples of your work. Generally used for professional appointments.