As mentioned above, when you first file a patent application for a particular invention, the date that the application is lodged with the Patent Office becomes the application’s priority date. It’s then possible, within one year of the original patent application filing, to file a subsequent patent application, for example an overseas patent application claiming the priority of the first filed patent under the Paris Convention.
Now it may be that after filing the first patent application, and before filing the overseas patent application, you have come up with an improvement to the invention that wasn’t described in the first filing. In that case a second patent application, for example a provisional patent application, may be filed describing the improvement. The overseas application would then claim priority from both the first patent application and also claim priority from the second application and the patent specification of the overseas application would describe and claim the material in both the first and second applications. The second patent application is effectively an updating provisional application because it updates the invention description of the first patent application.
No, provisional patent applications don’t ever get examined. They are simply filed with IP Australia and accorded a priority date and Australian application number. Provisional patent specifications are kept on file for thirty years before being destroyed.
The purpose of provisional patent application is to stake a claim, priority date wise, for a subsequent complete patent application. It’s the complete patent application that will actually be examined.