When we say that something is "a million light years away," it is a way to express an extremely vast distance in the context of astronomical measurements. A light-year is a unit of distance that represents the distance that light travels in one year, which is approximately 9.46 trillion kilometers or 5.88 trillion miles.
So, if something is a million light years away, it means that the light from that object has traveled for one million years to reach us. This distance is incredibly large on a human scale, considering that light travels at a speed of about 299,792 kilometers per second (186,282 miles per second).
When we talk about distances in the cosmos, the scale becomes so vast that using kilometers or miles would become impractical. Light-years provide a convenient way to comprehend and express such enormous distances. It allows us to understand how long it took for light, which is the fastest known entity, to travel from the object to our observation point.
To put it into perspective, our Milky Way galaxy has a diameter of about 100,000 light-years. So, when we say something is a million light years away, it implies a distance much greater than the size of our own galaxy. It helps to illustrate the immense size and scale of the universe.