JIT (just-in-time) is a CLR’s (Common Language Runtime) compiler. The JIT Compiler function is responsible for compiling a method’s IL code into native CPU instructions. Because the IL(intermediate language) is being compiled "just in time," this component of the CLR is frequently referred to as a JITter or a JIT compiler.
When JIT called, the JIT Compiler function knows what method is being called and what type defines this method. The JIT Compiler function then searches the defining assembly’s metadata for the called method’s IL. JITCompiler next verifies and compiles the IL code into native CPU instructions. The native CPU instructions are saved in a dynamically allocated block of memory. Then, JITCompiler goes back to the type’s internal data structure and replaces the address of the called method with the address of the block of memory containing the native CPU instructions. Finally, JITCompiler jumps to the code in the memory block. This code is then implementation means particular code get executed.




