What is a Prism in WPF?

Prism is also known as Composite Application Guidance for WPF and Silverlight. It is a framework that can be used to build Silverlight apps and WPF. It has been designed to build solid applications in Silverlight and WPF that normally have a single code base. It is helpful in developing a client application, which is in a modular fashion. It is done so to divide large, complex applications into simple modules. The actual definition of a Prism being

“ Prism is developed by Microsoft Patterns and Practices and provides guidance designed to help you to more easily design and build rich, flexible and easy-to-maintain Windows Presentation Foundation (WPF) desktop applications. ”

it was initially called Prism but later on, Microsoft named it as ‘CompositeWPF’.