Mmm thats a seriously great question that was a lot more complicated to answer then we originally anticipated!
If you just used a suburb as your search criteria, the short version is Google in most instances uses the location of the official Post Office to determine where to calculate distances from.
If you used an exact address then it will calculate the distance exactly from your address, typically 'as the crow flies' meaning in a straight line to that location. In other words it doesn't calculate the route you would have to travel to get there.
If you wanted to work out how long your daily commute would be then we suggest using Google Maps or your local state public transport planner:
- New South Wales
- Western Australia
- Australian Capitol Territory
- Northern Territory