So I was reading the javascript file of a website and I saw a variable wrapped in square brackets, can someone explain to me what and why that is? I do understand the whole code and what It does except for that part. The variable I'm talking about is 'entry'.

const fadeIn = function (entries, observer) {
  const [entry] = entries;
  if (!entry.isIntersecting) return;
  entry.target.classList.add("scroll-reveal");
  observer.unobserve(entry.target);
};

const observer = new IntersectionObserver(fadeIn, {
  root: null,
  threshold: 0.5,
});

reveals.forEach((curr) => {
  observer.observe(curr);
});