The vast majority of Australian borrowers get home loans with 30-year loan terms. This is the maximum amount most lenders allow. But it is possible to get a loan with a longer term of 40 years. A 40-year home loan is otherwise identical to other home loans: You borrow money and pay it back with interest charged on top.
The difference is the time involved and the amount of interest you pay. The main benefit for borrowers who take out 40-year loans is that they pay reduced ongoing repayments, as the debt is structured over a longer time period. The main drawback is that because they have their loan for longer, they end up paying a higher amount of interest in total.
It's a really good idea to talk to a mortgage broker before committing to a 40-year home loan.