Public Holidays in Australia consist of both National and Local public holidays, and therefore differ in each State / Territory.
As a general rule, employees are not required to work on public holidays, however in some cases working on a Public Holiday is necessary - eg. a Retail environment where the shops open on a public holiday, similarly in a hospitality environment where a hotel or restaurant is open on a public holiday.
If a public holiday falls on a day you would ordinarily work, and you are not required to work (and you are not a casual employee), you would generally be paid for the hours you would ordinarily work on that day.
Employees who are required to work on a public holiday get paid at least their base rate for all hours worked.
Awards, enterprise agreements and other registered agreements can provide entitlements for working public holidays including:
Source and additional information: https://www.fairwork.gov.au/leave/public-holidays/working-on-public-holidays
Details on all Public Holidays for all States & Territories in Australia can be found on the Fair Work Australia website: https://www.fairwork.gov.au/leave/public-holidays/list-of-public-holidays