Invoice:
invoicing is the process through which many companies claim payment for goods delivered or services rendered. At the point in the transaction in which both sides agree that the goods or work meets the stipulated conditions, the company performing the work delivers an invoice to the company receiving the work.
http://www.touchfinancial.co.uk/knowledge-centre/glossary/
Invoice must be submitted in duplicate to address indicated on face of Purchase Order. Invoice must state list price, discount allowed, net price, and PO number. Send a separate invoice for each shipment.
http://www.erau.edu/er/purchasing/terms.html
http://www.office-kit.com/billing_software/invoice_sample_lo...

Posted:
refers to the actual revenue and expense transactions, or purchase order encumbrances, that have been fully processed. These transactions have been entered into or "posted" to the General Ledger (GL).
http://comptroller.illinoisstate.edu/faculty/datatel/glossar...

"invoice is posted" image examples:
https://help.sap.com/saphelp_globext607_10/helpdata/en/48/b7...
http://www.sdc.ca/support/glp_acctreceiveforignexch.shtml
http://sdc.ca/sdc6/help/Accounts Receivable Foreign Exchange...
http://www.cnp-x.com/userguide/accounting/add_edit_del_billi...