What is the difference between var, let, and const in JavaScript?

// var: Function-scoped or globally-scoped
        var x = 10;
        if (true) {
            var x = 20; // Same variable, x is overwritten
        }
        console.log(x); // Outputs: 20

        // let: Block-scoped
        let y = 10;
        if (true) {
            let y = 20; // Different variable, scoped to the block
        }
        console.log(y); // Outputs: 10

        // const: Block-scoped, cannot be reassigned
        const z = 10;
        // z = 20; // Error: Assignment to constant variable
        console.log(z); // Outputs: 10