An Expression is way which is used for to perform a particular action. In computer science all the function and processes are performed in the form of Expression which is easily understandable for computer machine. In the Expression number of variables or constants, and operators and functions, are put together in a single statement that is acted on by a particular programming language. The evaluation produces a return or result. Simple mathematical equations such as 2 + 2 are Expression in code called arithmetic Expression. Expression is computer understand language in which we can run programming instruction to perform action. Different-2 programming language compiler's have different-2 Expression from. It same as Syntax of instruction.