A Digital Elevation Model, commonly referred to as a DEM is a digital representation of the height of the bare earth. Amongst other things, it can be used as the starting point for creating contour maps.
The state of NSW (Australia) is well served with Digital Elevation Models (DEMs). The entire state has coverage of at least 5m resolution, with most of the eastern ranges having 2m, and the east coast having 1m resolution.
Downloading the data is fairly straightforward, using the Australian Government's ELVIS service.
You will get an email shortly with instructions of how to download your data.
The data now comes as zipped .TIF files. Extract the .TIF files to a folder, and then you can drag them into QGIS.