Enterprise Library

        Enterprise Library is a collection of application blocks intended for use by developers who build complex, enterprise-level applications.

        Enterprise Library is used when building applications that are typically to be deployed widely and to interoperate with other applications and systems. In addition, they generally have strict security, reliability, and performance requirements.

The goals of Enterprise Library are the following:

Consistency. All Enterprise Library application blocks feature consistent design patterns and implementation approaches.

Extensibility. All application blocks include defined extensibility points that allow developers to customize the behavior of the application blocks by adding their own code.

Ease of use. Enterprise Library offers numerous usability improvements, including a graphical configuration tool, a simpler installation procedure, and clearer and more complete documentation and samples.

Integration. Enterprise Library application blocks are designed to work well together or individually.

This is referenced from MSDN Documentation:
http://msdn.microsoft.com/en-us/library/ff648951.aspx