When we say that a galaxy is 5000 light years from earth we are actually describing

A light year refers to a very big amount of distance and is a measurement termed as an astronomical unit of measure. When you say that a galaxy is 5,000 light years away we are actually describing the speed of light within a year. One light year is actually equivalent to 9, 500, 000, 000, 000 kilometers. Just imagine how big or how far that galaxy is when you multiply those kilometers by 5,000?

Hagrid's right, it defines withing the speed of light within a year.