From Wikipedia:
The Office of Film and Literature Classification was a statutory censorship and classification body overseen by the Australian Government which included: the Classification Board which classified films, video games and publications for exhibition, sale or hire in Australia; the Classification Review Board which reviewed previously classified films, computer games and publications on appeal; and administrative staff who provided day to day support for the two Boards under the control of the Director of the Classification Board.
M – Mature: Despite the title, material classified M15+ is not recommended for people under 15 years of age. Nonetheless, there are still no legal restrictions on access. This rating has since been changed to M to prevent confusion with the stronger MA15+ classification.