A VPN works by connecting your computer (using encryption) to another computer located somewhere else in the world. Your access to the internet then comes from that computer located somewhere else in the world. So if the computer is located in France, then you are surfing from France. This simple technology thwarts the mandatory data retention scheme implemented by the Australian government. This also makes it harder for you to be tracked generally. Be warned that this alone will not offer substantial protection if you are subject to a targeted digital investigation. As an added bonus a VPN allows to to access content that has been geographically restricted such as the BBC.
There are many companies providing VPN services. Some may be owned by the intelligence community or dodgy in some way. Do a bit of research before choosing your VPN provider.
A decent VPN will cost some money and we recommend this spend.