Cash Sales (a.k.a Sales Receipts in Quickbooks) are used to record the immediate sales of Items for payment.
The Customer, Items, and payment method are recorded on the Cash Sale document.
Configuration
If 'Invoice non-allocated lines' is enabled in Setup > Configuration > Sales Order, users may create a Cash Sale for an Order with items that have not yet been allocated. The order status will remain as 'Open' until all items are allocated and shipped, at which point, the status will change to 'Fulfilled.'