Motivation
Maps many to many association in between the tables (Link Table Mapping).
Summary
Association table is a link table that just contains IDs of Foreign keys of tow tables.
In Business object it is mapped with tow way "Foreign Key Mapping" approach i.e. parent to child and child to parent.
ORM Frameworks like EF provides out of the box implementation for such cases
Data Model
Business Model
When to Use
whnt you have many to many mapping in between data base tables
References