AP is an Enterprise Resource Planning (ERP) system. It is an IT based transaction processing system. All business processes are executed in one system sharing common information.
SAP - TM - Travel Management (T) - SAP - BP - Travel Planning - Chapter 2 - PART C - Car Rentals
SAP ERP FICO (Finance) is a Fiscal Year Variant contains the definition of Posting Periods and Special Periods. It also determines whether the fiscal year is based on calendar year - i.e. Jan - Dec or non-calendar year e.g. Apr - Mar.
Chapter 22 - SAP ERP FI (Finance) Sort Keys, Line Layout and Total Variants
SAP ERP - FI (Finance) - Document Entry
SAP ERP - FI (Finance) Accounts and Balance display