Recent Purchases (or Invoice) Tab

The Recent Purchases tab shows you items the customer has purchased in the past with the most recent items first. This lets you quickly create an order when the customer says "I want some of the same things I bought last time."

Invoice (Applied Credit Memo)
If this is a credit memo applied to a specific invoice then this tab shows only the items purchased on that invoice. This lets you quickly select which items are to be returned via the credit memo.