The Common Language Infrastructure (CLI) is an open specification developed by Microsoft that describes the executable code and runtime environment that allows multiple high-level languages to be used on different computer platforms without being rewritten for specific architectures. CLR is Microsoft Commercial implementation of Common Language Infrastructure (CLI).
The Common Language Infrastructure (CLI) is a theoretical model of a development platform that provides a device and language independent way to express data and behavior of applications.
While the CLI primarily supports Object Oriented Programming (OOP) languages, procedural and functional languages are also supported. Through the CLI, languages can interoperate with each other and make use of a built-in garbage collector, security system, exception support, and a powerful framework.