Application Module & its types

Application Module :it is the interface between database transactions and UI transactions .
  All the application model objects end with AM ex- Employee AM.

 Types of application Modules: 1)root application module 2) Nested application module

 1)root application module:attaching AM to the root region we call as root AM ,where root region is the page layout region.

2)Nested application module:Attaching AM to the nested region we call as the nested application module where nested region are like child regions.

**If we declare vo at Root AM we can use it any where , but if we declare VO at region level we can use only for the particular region**