You will want to create variables for many reasons. You will need it to hold user input, arguments, or numerical values. There are two types of variables. Local variables, and environmental variables. Environmental variables are set by the system and can usually be found by using the env command.
Environmental variables hold special values.
The echo command is good for checking the current value of a variable, environmental, or local. Okay, now suppose you decide that you want the value of x to be 8 instead of 12. You have to change all the lines of code where it says that x is 12. No, because they are not associated with x . The other lines will be unaffected.