Check CAR 1988 Part 5 on the CASA website,
www.casa.gov.au; your licence is valid for good unless you get it taken away for some reason, but to exercise the rights and privileges of it you need to undergo a flight review every 2 years (was called BFR but now AFR or HFR as appropriate for fixed wing or helicopter).
Can be done by a grade of flight instructor (Australian licenced)who is authorised to conduct flight reviews (check the orders for fixed wing, for helicopters it's Grade 1), and that instructor also needs to be working for a flying school or have an agreement with one to conduct flight reviews (according to the definition of an authorised flight instructor in the CARs).
The format of the flight would vary depending on who's conducting it, but I'd suggest you'd have to perform competently in some or all of the following: normal, flapless and glide circuits, general handling, airspace and navigation requirements to and from the training area if used (or further afield), accurate flying within the limits expected on your licence test, steep turns, stalls, and of course emergency procedures such as practice forced landings, systems failures (eg gear if applicable, various engine abnormalities and so on).
The check is not necessarily supposed to be a pure test; ie, if you stuff something up the instructor would be allowed to treat it as a learning point and provide input to get you up to speed, but in the end, you would need to perform to the required standard in order to successfully complete the flight review.
Doing a rating (eg NVFR, instrument) also counts as a flight review so you can kill two birds with one stone in some circumstances.
Hope that helps; have a read of the orders too and refresh your memory.