Explain Like I'm Five

The light takes the same amount of time to get there from an external point of view. It's more like time slows down for you the faster you go, which from an external perspective would look like you moving and acting slower than normal. So in the time it would take light to travel 1 light year, it always takes one year. However, you would be slowed down so much that it would appear to you that much less time had passed, maybe only a few days. If you travel at the speed of light you slow down so much that no time passes for you at all at that speed. So you instantly arrive, from your point of view. However, from the point of view of an external observer, it still took one year.

Essentially, it slows down the amount of time you experience, but the amount of time that actually passes externally doesn't change. If you go to the moon, it will take only 1 second at light speed, so you wouldn't really notice whether it felt instant or to take a second. However, if you go somewhere further like Proxima Centauri, which is 4 light years away, you will arrive back on Earth at least 8 years later (there and back). If you go at light speed, it would appear to be instant, suddenly you're at Proxima Centauri 4 years later, suddenly you're back at Earth 8 years later. If you go just below light speed, you'll see the world outside go past like it's being fast forwarded, and when you return, 8 years will have been compressed into something that seems much shorter to you.