This is the root of the persistent ID (PID) URI DNS subdomain used by Geoscience Australia to both identify and provide access to a range of digital resources such as datasets, vocabularies, terms within vocabularies, list of people and systems, etc.
The choice of this subdomain for PID use, rather than GA's web address, www.ga.gov.au, is in accordance with 'Cool URI' principles, in particular that PID URIs shouldn't include organsational details that are liable to change with organisational change, such as the 'ga' for GA. Since this domain, geosceicne.gov.au, is concept-based, it's likely to remain relevant to Australia for all time (or at least for as long as Australia exists!).
The PIDs within this domain and associated resources, such as this web page, are maintained by Geoscience Australia's Scientific Data section on behalf of the agency and the Australian geoscience community as a whole.