let is similar to var but let has scope. let is only accessible in the block level it is defined
<script>
if (true) {
 let a = 40;
 console.log(a); //40
}
console.log(a); // undefined
</script>

In the above example variable ‘a’ is defined inside If statement and so it’s not accessible outside the function.

<script>
	let a = 50;
let b = 100;
if (true) {
 let a = 60;
 var c = 10;
 console.log(a/c); // 6
 console.log(b/c); // 10
}
console.log(c); // 10
console.log(a); // 50
</script>5