SNOMED CT-AU is the Australian extension to SNOMED CT, adding Australian-developed terminology to the core international data, as well as the Australian Medicines Terminology (AMT). The AMT is now included as a formal subset of the SNOMED CT-AU release in preparation for future integration work. It is no longer provided as a stand-alone RF2 file for download.
Not sure which format to download or the differences between them? The LEARN section provides an overview of each format type.