The most relevant regulation today is the Road Rules which are now pretty
standard in every State and Territory because they are required to be
conisistent with the Australian Road Rules that were agreed upon by all
jurisdictions. The NSW RMS Technical Direction, posted here recently by
Greg, provides and explains the definitions:

https://www.rms.nsw.gov.au/documents/business-industry/partners-and-suppliers/guidelines/ttd_2017-002.pdf

A Tram Lane is a road lane.

A Tramway is basically enclosed by or alongside a roadway and is separated
by line markings (double yellow lines) or some structure or physical
obstacle which may range from a simple berm to a median or vegetated strip.
So, for example those tracks sauntering along the middle of a highway in
what appears to be a reservation are a Tramway. As soon as they head away
from a road reservation they are off-road and outside the road traffic
jurisdiction, so nowadays I suppose we'd call that bit light rail, though
nobody would bother using that term with a short section.

Tram Lanes and Tramways can also be used by public buses and tram recovery
vehicles.

In Sydney, IWLR is light rail, reliant entirely on its own safeworking,
west of Darling Drive. East of Darling Drive to Central it is a Tramway.
CSELR is almost entirely a Tramway except around the Moore/Centennial Park
area, subject to seeing what the final line markings are, but I think they
wouldn't be allowing general traffic to have any reason to encroach on the
line.

Tony P