Arrangement: While working on a application you may have used some predefined values. The visibility of these values can be application level, feature level or class level. For the convenience we give name to these values and then use in the application. In this case the name given by you only representing the single value and it never change to represent some other value thats why it is called Constant. On the other hand variables are like us doing jobs in IT World and can switch from one organization( value ) to other. Like while choosing a partner for marriage you may choose best for you by seeing multiple persons and still after sometime you feel stuck. Same may happen you choose a best option to declare a constant and after sometime this constant can create a issue for you in code due to its scope or any other reason. On the other hand you may have a fixed mind that you always declare a constant in a same way in any situation like a love marriage and again after