What it is for. Billing the same client the same amount on a schedule — a monthly maintenance contract, a quarterly service fee — without having to remember.
What you see. One card per schedule: the customer, the amount, the cycle and the next date. Run due now processes anything due today; Generate now on a single schedule bills it off-cycle.
Worth knowing. A schedule set to auto-send creates the invoice as Sent, which means it appears in the client's portal immediately. A schedule without it creates a draft for you to review.