The Payables and Receivables lists contain a historical record of everything related to your payables (Bills) and receivables (Invoices), respectively. While they can provide direct access to records, they are mostly there to be used as a tool for auditing or otherwise double-checking on operations performed in other Administration modules.
Both lists can be searched, which can help get a quick snapshot of interactions with a particular Vendor or Customer — or to ensure that a particular Bill or Invoice has been processed as expected.