The Census is a count of every person in Australia. The Australian Bureau of Statistics runs it every five years. It aims to count everyone on a single night. It records age, sex, where people live, housing, work, and more.
The ABS counts people where they are on Census night. This is the place of enumeration. But what matters for estimates is where people usually live. The ABS fixes the counts to match usual residence after the fact.
No census is perfect. Some people are missed. The ABS runs a Post Enumeration Survey after each one to measure the gap.
Census data is the starting point for most of what Place Forecast shows. Population counts feed into the estimated resident population. Dwelling counts become the census dwellings base. Each new Census gives a fresh set of figures. The ABS then rebases all estimates to line up with the new count.