Main difference is scoping rules. Variables declared by ``var`` keyword are scoped to the immediate function body (hence the function scope) while ``let`` variables are scoped to the immediate enclosing block denoted by `` { } `` (hence the block scope).

```typescript

function run() {

var foo = "Foo";

let bar = "Bar";

console.log(foo, bar);

{

let baz = "Bazz";

console.log(baz);

}

console.log(baz); // ReferenceError

}

run();

```

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