In simple terms var is function scoped and let is block scoped.
var
- var variables can be globally accessed
 - var variables can be re-declared
 - let and var variables work the same way when used in a function block.
 
let
- let variables cannot be globally accessed
 - let variables cannot be re-declared
 - let variables are usually used when there is a limited use of those variables.
 - let and var variables work the same way when used in a function block.
 
'use strict';
let me = 'foo';
let me = 'bar'; // SyntaxError: Identifier 'me' has already been declared 'use strict';
var me = 'foo';
var me = 'bar'; // No problem, `me` is replaced.  Thank you so much for reading.
