The BI Presentation Services and BI Server are the two key components of the OBIEE Architecture. The BI Server connects to a wide variety of data sources, but integrates the data it retrieves using a mapping held in a local data store, the BI Repository, so that to its client applications it appears to contain a single table with a large number of columns. This semantic view of the enterprise’s data is presented to end users by the BI Presentation Services and is the basis for constructing ad hoc queries.
Oracle also provides "BI Applications" using the OBIEE Architecture that comprises of a Pre-Packaged Repository, Pre-Packaged set of Reports for a particular ERP, Business Analytics Warehouse, Informatica ETL and a DAC ETL Orchestration Server.
The BI Applications is a high-end BI Solution from Oracle that will get users up and ready very quickly by avoiding custom-building a solution with just a OBIEE Server.