Common Language Runtime (CLR) is a virtual machine used as part of Microsoft's dot NET framework. It improves performance by providing a richly interact between programs at the run time. The CLR uses just in time compilation to execute the compiled code of dot NET applications regardless of what programming language was used.
It runs the code and provides services that make the development process easier, provides class libraries support to an application when needed. The main function of Common Language Runtime (CLR) is to convert the Managed Code into native code and then execute the Program. Basically, it is responsible for managing the execution of dot NET programs regardless of any dot NETprogramming language.