Let's suppose you had a gigantic zoom lens — so big that you could effectively zoom as far as you wanted to frame any object. If you pointed it into space, how far could you see? It turns out that you could see a really long way away and yet, not that far at all.
Coming to you from Real Life Lore, this fun video explores the concept of the observable universe. The observable universe is simply how far (if given unlimited technological means) we could see into space, which is limited by light needing to have had sufficient time to travel the distance to reach Earth. Thus, you might simply assume it's 13.8 billion light-years in all directions given the universe is 13.8 billion years old. The problem is that cosmological expansion has pushed things apart since essentially the beginning of the universe. Thus, we can measure light from objects that were once closer, raising the radius to 45.7 billion light-years in all directions. That's about 268,700,000,000,000,000,000,000 miles if you prefer those units. So why would I possibly call that a small distance? It turns out that that's merely a fraction of the total size of the universe. Check out the video above for more.