I am travelling from Johannesburg to Auckland via Abu Dhbai, Singapore and Brisbane. I know a lot of flying and stops but I don't mind as I love flying and the prices were very cheap. All flights booked as one ticket. I only have a 1 hour and 40 minutes in Brisbane before connecting from Etihad to Air New Zealand. I often here that the flight from Abu Dhabi to Brisbane Via Singapore is delayed. If my flight was delayed and I missed my connection to Auckland would they put me on the next available flight for free?
If it's all one one single ticket, then you'll be fine, and re-booked onto the first available later flight if you miss your connection. (Note that first available flight may not be the next flight, depending on if the next one is full or not)
If you book it as two tickets, then it varies by airline. Some airlines have stated policies of accommodating passengers one two different tickets where both are with that airline, and one flight is late. Some (eg most LCCs) explicitly have a policy that they won't. Chances of free rebooking drop dramatically if there are two airlines involved and on two tickets, if changing airlines allow lots of time or book as a single ticket! If booking as two tickets, check with the airline(s) first!
Additionally, if you are delayed and miss your onward flight, depending on the countries in question and airlines you might be entitled to compensation, hotels, food etc. That all depends on the regulations governing your flight. Were there EU bits involved, then that'd be EU-261, but since you're worried about a connection in Australia then you're a bit out of luck as Australian regulations don't (currently) provide the same level of protection. You'd likely mostly be reliant on your travel insurance here, plus airline good-will, so probably best to ensure you have a decent level of cover in place!