If a star is 4 light-years away, what does it mean?

If a star is 4 light-years away, it means that the distance between Earth and the star is so great that light traveling from that star takes four years to get to us. When you look at the star, you are actually seeing it as it was four years ago, because that’s how long the light has been traveling through space to what you see now. This concept is important in astronomy because it also means we’re looking back in time when we observe distant objects—all their light comes to us after traveling those huge distances.​