3/ Database Layer
In this layer al the persistent data is stored in a database.
It 's managed by an RDBMS:
Relational Database Management System
E.g.: SAP HANA, Oracle, MSSQL, SAP MaxDB, ..
/7 Forms
For pulling data out of the database and present it to a user, but unlike reports it is not used to present the data in a report output but in a form output.
Typically used when a physical version of documents is needed (e.g., invoices).