What precisely is a Light Year?

A light-year is the DISTANCE which light can travel in a year. As light is fast, a lightyear is a long way! The speed of light is exactly 299,792,458 metres per second. In a year there are 60 x 60 x 24 x 365.2425 = 31,556,952 seconds. So how far is a light year? Answer: 9,460,536,207,068,016 metres. About 6 million million miles.