In a survey, only part of the total population is selected. The survey data is then used to make inferences about the whole population, providing a reasonably reliable picture of that population. Most ABS findings are based on surveys, covering such topics as household expenditure, employment, crime, etc.
A census collects information from every unit in a population. As a result, data is truly representative of the whole population and detailed accurate data can be made available right down to small areas.