A light-year is a unit of length, similar to a meter or a foot. Meters and feet are commonly used to measure small distances, such as the distance between two cities or the height of a person. In contrast, light-years are used to measure vast distances in space, such as the distance between stars and planets.
Now this is where it gets tricky.
Light-year is the distance travelled by light in a Julian year (365.25 days).
So how is it not a unit of time but a unit of length? We multiply the number of seconds in a Julian year by the speed of light (the distance travelled by light in a second). Which is-
31,557,600 seconds (no. of seconds in a Julian year) * 299,792,458 meters per second (speed of light)
Then we get the value of a light year in meters. Which means that if the distance between two bodies is a light year, then the distance between them is-
9.461 × 10^15 meters (9.461 quadrillion meters); or
9.461 trillion kilometres(5.879 trillion miles)
If you travel from location A to location B at a certain speed and in a certain period of time. This distance is the distance you have travelled, which also makes it the distance between locations A and B.
The same way this is the distance light travels in a year.
I hope this helps. If you need any help or have a problem understanding any of these things let me know in the comments.
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