One of the problems in the existing database model is data being left behind when an application is moved from one instance to another. Some data connected with an application, (for example, login information and agent job information) is currently stored within the instance instead of inside the database and When you move a non-contained database application from one instance to another instance of SQL Server, this data is left behind.
Later on, DBA's need to identify the data which was left behind and move it with the application to the new instance of SQL Server. This process can be time consuming and difficult.
This is where Contained Databases will be really useful.
Separates the database application from the management of SQL Server
Users can connect to the database without authenticating a login at the Database Engine level
Applications within contained databases can be isolated from other databases from the instance of SQL Server, on which they reside, simplifying development and management