Oracle Purchasing Tables

Usual Oracle Applications PO Tables
PO_HEADERS_ALL: Purchase Order information with Supplier, Site and status
PO_LINES_ALL: PO Lines with Item Information and quantity
PO_LINE_LOCATIONS_ALL: PO Information on Shipments Destination
PO_DISTRIBUTIONS_ALL: PO Distribution where the accounts are
PO_LINE_LOCATIONS_ARCHIVE_ALL: table updated for history on Shipment/Destination Location Information
PO_LINE_TYPES_B: PO Types used in the PO_LINES_ALL
PO_LINES_TYPES_TL: PO Line Types used in MLS 
PO_RELEASES_ALL: Stores revision number for the PO
PO_HEADERS_ARCHIVE_ALL: table updated for the history on the status and PO Header changes, Lines, Location and PO Accounts Distribution
PO_LINES_ARCHIVE_ALL: table updated for the history on the lines
PO_DISTRIBUTIONS_ARCHIVE_ALL: table updated for the history on the account distribution
PO_AGENTS_V: Buyer
PO_VENDORS: Supplier Table
PO_VENDOR_SITES: Supplier Sites
PO_VENDOR_CONTACTS: Supplier Contacts

PO_HAZARD_CLASSES: contains code and description for hazardous items which gets automatically printed into purchase order, RFQ and Receipt Travelers

PO_REQUISITION_LINES_ALL: Requisition Lines
PO_REQUISITION_HEADERS_ALL: Requisition Headers
PO_REQ_DISTRIBUTIONS_ALL: Distribution Lines of Requisition where accounts are
PO_APPROVED_SUPPLIER_LIST: Supplier List for Auto-Sourcing
PO_ASL_DOCUMENTS: Advanced Shipment Documents
PO_APPROVAL_LIST_HEADERS: PO Approval Path
PO_APPROVAL_LIST_LINES: PO Approval Path

OTHER RELATED: 
MRP_SOURCING_RULES: Used for Auto-Sourcing Rules
MRP_SR_RECEIPT_ORG: Used for Auto-Sourcing Rules
MRP_SR_SOURCE_ORG: Used for Auto-Sourcing Rules
MRP_ASSIGNMENT_SETS: Used for Auto-Sourcing Rules
MRP_SR_ASSIGNMENTS: Used for Auto-Sourcing Rules
RCV_SHIPMENT_HEADERS: Shipment Table Header with grouping information
RCV_SHIPMENT_LINES: Shipment Table lines with item information
RCV_TRANSACTIONS: PO Lines or Requisition received in destination or transit
RCV_ACCOUNTING_EVENTS: Receiving information on accounts
RCV_RECEIVING_SUB_LEDGER: Accounting entries generated for the receiving transactions
RCV_SUB_LEDGER_DETAILS: Detail accounting entries generated for the receiving transactions 
RCV_LOT_SUPPLY: Parent for RCV_LOT_TRANSACTIONS
RCV_LOT_TRANSACTIONS: Table housing the information what lot the item is received

INTERFACES:
PO_HEADERS_INTERFACE: Used for creating PO
PO_LINES_INTERFACE: Used for creating PO
PO_DISTRIBUTIONS_INTERFACE: Used for creating PO
PO_REQUISITIONS_INTERFACE: Used for creating Requisition
PO_REQ_DIST_INTERFACE: Used for creating Requisition
PO_INTERFACE_ERRORS: Error created during the processing of the PO or requisition
RCV_INTERFACE: Used for creating Received Items
RCV_HEADERS_INTERFACE: Used for creating Received Group of items
RCV_LOT_INTERFACE: Used for receiving item into a particular lot

References:

http://oracleexpertsolutions.blogspot.com/2011/03/purchasing-tables.html