If you have a standard policy, your car is covered no matter who is driving (with a few exceptions).
If you have a Nominated Driver policy, drivers under 25 aren’t covered (except learners accompanied by a fully licensed driver over the age of 25). Also, if someone’s driving and they’re not listed on your Nominated Driver policy, you’ll pay a higher excess if you make a claim.
Your can find more information in the Motor Vehicle PDS.