Welcome to QuickBooks Online, @Kimp22. I'll share some information about the difference between an invoice and a sales receipt in QuickBooks Online.
When a consumer agrees to pay you later, you send them an invoice. You can establish terms to tell the customer how long they have to pay. Their invoice will be considered late if they do not pay within the given time frame. While your customer pays you for goods or services on the spot, you issue a sales receipt.
You can check this article for additional information about the invoice and sales receipt.
I'll provide these links that will guide you how to create an invoice and how to record invoice payments in QBO.