Dwellings density is the number of dwellings per hectare of land. Place Forecast works it out as the dwelling count divided by the land area in hectares. The unit is dw/ha, a common way to express dwelling density in Australia.
Zoning controls are usually expressed at net density. Net density is measured at the lot scale and leaves out roads and reserves. This page shows gross density across the whole area boundary. The two are not directly comparable.
A few things matter when you read dwellings density:
Density is not the same as crowding. Crowding is about how many people share a home. Density is about how dwellings spread over land. A place can be dense but not crowded.
Spatial dwellings density is not the same as structural density. Structural density is the share of medium or high density dwellings, that is on the Dwelling Structure Rate page. This page is about how many dwellings sit on the land, regardless of structure type.
The land area is gross. It includes parks, water, and unused land.
The land area stays fixed. Only the dwelling count changes over time.