Explain the difference between let and var in Swift Programming?

Both the terms 'let' and 'var' are used for declaring the functions in JavaScript but the main difference between these two terms is that the 'let' is block scoped while a 'var' is the functional scope. It is not wrong to say that a variable represented with var is defined throughout the program in relation to let

Example of var:

Input: 
console.log(x); 
var x=5; 
console.log(x); 
Output: undefined 5

Example of let:

Input: 
console.log(x); 
let x=5; console.l
og(x); 
Output: Error