What are the differences between let and var in JavaScript? Explain with examples

Hello! I started learning JavaScript and encountered some confusion. I know that previously everyone declared variables using `var`, but now modern tutorials recommend `let`. They seem to do the same thing — create variables. But when I write code, they behave differently. Here's an example that confused me: ```javascript var x = 10; if (true) { var x = 20; // I thought this was a new variable console.log(x); // 20 } console.log(x); // 20 — why not 10? ``` If I replace `var` with `let`: ```javascript let x = 10; if (true) { let x = 20; console.log(x); // 20 } console.log(x); // 10 — and here it's 10, as expected ``` Why does this happen? And I also heard about "hoisting" — is that related somehow? Please explain for a beginner when to use