ES6 introduced the keywords let and const that enable us to declare variables much easier.
Previously, variables declared with var are function loop they will be scoped, so if we declare them inside a for loop they will be available outside of the loop.
Variables declared with let and const are block-scoped, which means they are only accessible within the block where they were declared.
So, if we declare a variable with let, it does not change its value in the outer scope.
const is similar, but the value of variables declared with this keyword cannot change through reassignment.