Application virtualization is an umbrella term that describes software technologies that improve portability, manageability and compatibility of applications by encapsulating them from the underlying operating system on which they are executed. A fully virtualized application is not installed in the traditional sense, although it is still executed as if it were. The application is fooled at runtime into believing that it is directly interfacing with the original operating system and all the resources managed by it, when in reality it is not. In this context, the term "virtualization" refers to the artifact being encapsulated (application), which is quite different to its meaning in hardware virtualization, where it refers to the artifact being abstracted (physical hardware)
The basic concept of Application Streaming has its foundation in the way modern computer programming languages and operating systems produce and run application code. Only specific parts of a computer program need to be available at any instance for the end user to perform a particular function. This means that a program need not be fully installed on a client computer, but parts of it can be delivered over the network as and when they are required.
ref:
Application Virtualization - http://en.wikipedia.org/wiki/Application_virtualization
Application Streaming - http://en.wikipedia.org/wiki/Application_streaming
MSDN Webcast: Application Virtualization And Software Streaming Within Systems Management Server (Level 200) - http://www.techrepublic.com/whitepapers/msdn-webcast-application-virtualization-and-software-streaming-within-systems-management-server-level-200/355156
Application Virtualization for Developers - http://msdnrss.thecoderblogs.com/2011/04/application-virtualization-for-developers/
Microsoft Application Virtualization (App-V) - http://www.microsoft.com/en-us/windows/enterprise/products-and-technologies/virtualization/app-v.aspx
Application Virtualization Smackdown - http://www.brianmadden.com/blogs/rubenspruijt/archive/2010/09/22/application-virtualization-smackdown-head-to-head-analysis-of-endeavors-citrix-installfree-microsoft-spoon-symantec-and-vmware.aspx
Application Virtualization with Microsoft Dynamics NAV 2009 R2 - http://msdn.microsoft.com/en-us/library/gg670186.aspx
