Wanted to share here, the simplest explanation that I have ever seen on the web, for the famous Closures topic. (Credits : roadmap.sh)

A closure is a function that has access to its outer function scope even after the outer function has returned. This means a closure can remember and access variables and arguments of its outer function even after the function has finished.

function outer() {
  const name = 'Roadmap';

  function inner() {
    console.log(name);
  }

  return inner;
}

const closure = outer();
closure(); // Roadmap

In the above example, the inner function has access to the name variable of the outer function even after the outer function has returned. Therefore, the inner function forms a closure.