Select Accrual Accounts Question

Hi,

The Inventory Accrual Account is setup at Inventory Organization level and when doing an online receipt the account is credited. When an invoice is matched to a PO the accrual account is debited.

I see that in Purchasing there is a form Navigation Accounting > Select Accrual Accounts

When are these accounts used? In simple terms what is the functionality behind the setup of this accounts?

Thanks,

cv