A light-year is the distance that light travels in a vacuum in one Julian year (365.25 days). It's a unit of astronomical distance.

One light-year is equal to about 9.46 trillion kilometers.

Kilometers are too small a unit to practically measure the vast distances between stars and galaxies. Light-years provide a more manageable scale for these immense distances.

In the context of space, 1000 kilometers is a very small distance. It's only a tiny fraction of a light-year, which measures interstellar distances.