Selling isn't getting paid. The Cash Flow section shows you when the money from your sales will actually come in.
What does the report show?
A cash flow report over the range you choose (last 2 weeks, next 3 weeks, etc.) with: how much you sold, how much is payable, payment fees (amount and %), how much you've already collected and how much is still pending. You can view it week by week to compare what you received against what you sold.
Pending payments detail
In the detail view you see all pending orders with: order total, payable total, when the payment is scheduled, the total in installments and the payment breakdown (where and when the money comes in: Mercado Pago, Pago Nube, etc.). That way you know how much you still have to collect from sales already made and how much you'll receive from previous weeks.