"Good" vs "bad" debt
In the run-up to this year's budget, Treasurer Scott Morrison outlined that the budget documents would more clearly delineate the difference between what he calls "good" and "bad" debt.

"In this Budget we will be making changes to the way we report Government debt and link it to Government spending, by increasing the visibility on good and bad debt."

Treasurer Scott Morrison
Thursday 27 April 2017

What this change actually means is the government is reporting the net operating balance alongside the underlying cash balance.

The underlying cash balance counts things like revenue from government investments and tax. The net operating balance is usually healthier because it doesn't include some of the government spending measures (particularly one-off and short-term programs and investments).
A tale of two balances
Underlying cash balance 2017/18: -$29.4b
Net operating balance 2017/18: -$19.8b
Shifting the focus to the net operating balance makes it look like the budget is moving into surplus much quicker - particularly because the divide between the cash balance and the net operating balance is set to widen in the coming years.
Both balances over time
Net operating balance
Underlying cash balance