Well? No difference!!
One is the technical name and the other is the commonly used name.
Here in Australia, prenuptial agreements are binding financial agreements entered before the commencement of the marriage (or a de facto relationship).
Binding Financial Agreements are the more formal terminology that we use in Family Law. BFAs are often mistakenly referred to as a prenuptial agreement or a prenup.
A prenuptial agreement (or ‘prenup’) is made before the parties are married, but is generally seen as an American term and not an Australian term.
The equivalent of a prenup in Australia is known as a Binding Financial Agreement.
The legislation here in Australia, does not make any reference to the phrase “prenuptial” to draw the distinction that binding financial agreements are a completely different concept.