How do Closures work in JavaScript? Explain with a simple example

Hello everyone! I just started learning JavaScript and I can't understand the topic of closures. I read different articles, but I'm still confused. For example, there is this code:

function counter() {
    let count = 0;
    return function() {
        count++;
        return count;
    };
}

const myCounter = counter();
console.log(myCounter()); // 1
console.log(myCounter()); // 2
console.log(myCounter()); // 3

Why doesn't the count variable reset each time? After all, the counter() function has already finished its work, but we can still change its internal variable. I expected that after the first call to myCounter(), the count variable would be destroyed since it was declared inside the function. And another question: why are closures needed at all? In what real situations are they