Bill Transaction Creation on Billing Event Creation

Summary:

Just want to confirm if this specific feature is for billing events only or if for expenditure items that are billable

Based on the release notes, The Maintain Bill Transactions process (which was delivered in release 23C) has been extended to manage the automatic creation of bill transactions when billing events are created. You are not expected to schedule or routinely monitor the outputs of this process; the application launches it as and when needed. - Does this mean that billing events will automatically created as needed for the contract? What is the criteria and how it will be picked up?