Here’s a brief description of the terminology that is used in the Oracle BI Applications context.
Source Instance — The transactional system (that is, OLTP) that serves as the source of data for Oracle Business Analytics Warehouse. To read and analyze data from a source system, you must register it with Oracle BI Applications. You can do so by using Configuration Manager.
BI Application Offering — A BI Application product that you have purchased, for example, Oracle Financial Analytics or Oracle Sales Analytics. To start using a BI Application Offering, you must first enable it in Configuration Manager.
Functional Area — A component of a BI Application Offering. For example, the Oracle Human Resources Analytics Offering has Functional Areas: Workforce Effectiveness, Leave & Accrual, and Workforce Development. A Functional Area is the smallest unit that can be configured in a BI Application Offering.