losures are one of the most powerful concepts in JavaScript. A closure allows a function to remember variables from its outer scope even after the outer function has finished executing.

This is heavily used in modern frameworks like React. Many patterns such as hooks, event listeners, and private state rely on closures.

If closures ever confused you, the MDN documentation explains it very clearly:
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Closures

Once you understand closures deeply, many JavaScript behaviors suddenly make much more sense.