What is the difference between let and var in JavaScript?

Hi everyone! I just started learning JavaScript and encountered a situation I don't understand. When I declare variables using `var` and `let`, the code behaves differently, and I can't figure out why. Here's an example that confused me: ```javascript function test() { if (true) { var x = 10; let y = 20; } console.log(x); // 10 console.log(y); // ReferenceError: y is not defined } ``` Why is `x` accessible outside the `if` block, but `y` is not? I thought both variables were declared in the same place. Another example with a loop: ```javascript for (var i = 0; i < 3; i++) { setTimeout(() => console.log(i), 1000); } // Outputs: 3 3 3 for (let j = 0; j < 3; j++) { setTimeout(() => console.log(j), 1000); } // Outputs: 0 1 2 ``` Why does