Here is a link to a great high-level document on Windows Server AppFabric that is a great high-level guide to introduce you to Windows Server AppFabric.  David Chappell is a leading author in the industry and has a unique ability to simplify complex topics.  He also does a great job of helping you understand why you want to use this technology.

 This topic is a high-level overview.
Here we discuss theory and general concepts. Do not be too specific. Avoid referencing specific product names or procedures (except as required for examples).

One of the great truths of building software is this: Application developers shouldn’t spend their time creating infrastructure. Even though every application needs some supporting services, the people who write those applications ought to focus solely on creating value for their users. Whatever infrastructure is required should be provided by the platform they’re building on. Given this, one way to improve a platform is to provide better application infrastructure. This is exactly the goal of Windows Server AppFabric. By providing a set of extensions to Windows Server, Microsoft aims at making it easier for Windows developers to create faster, more scalable, and more manageable applications.

Windows Server AppFabric is provided as extensions to the Application Server role of Windows Server, and an application is free to use its parts separately or together. This introduction looks at both, describing what each one does and how it can be used.

 

Introducing Windows Server AppFabric

http://download.microsoft.com/download/7/F/8/7F8BD8A0-EB05-4DB5-A5A4-DD1D3C909A0A/Introducing_Windows_Server_AppFabric.pdf