The Federal Government's contact-tracing app has smashed expectations and has been downloaded more than two million times since its release.

It's hoped it will help track down contacts of confirmed COVID-19 cases, but there is still a lot we don't know about the app.

And is there any evidence that it will even help?

Today, Coronacast is joined by tech reporter Ariel Bogle from the ABC's science unit to help answer your questions.

On today's show:

* What is the COVIDSafe app supposed to do?

* Is it spying on me?

* Is being fit and healthy a good thing to help tackle coronavirus?

* What happened to all those suburb hotspots?

* Is there a possibility of infertility occurring from this virus?

And Dr Norman Swan has a study that dives into antibodies, which might give us some clues around immunity.