There is a PO Security code for Purchase Orders and an AP Security Code for Invoices. These security codes represent a department or division. It also drives approvals and limits users to view only information for that particular department or division.
There is also a PE Security Code for Vendors. Most users will only see INTERNAL(For Bill to and Ship To on an PO), EMPLOYEE(For Reimbursement Requests), and VENDORS(If they are Active).