Despite the word year in the term, it is not a measurement of time but a measurement of distance. So what's the use of an extra unit of measurement you ask. Well then here you go.
Let's take a example of width of the observable universe is 8.8 x 10^26 m. This number is so huge that it is unfathomable to us. So to understand that the lightyear term was introduced. So what's a light year. It's the distance travelled by light in a vacuum in a Julian Year (365.24 Days). So using this as the definition a light year would be 299792458 x 365 x 24 x 60 x 60 meters. Well that equals to 9.4 Trillion km. Yep it's that huge.
So with the definition of light year defined what will be the width of the observable universe in lightyears? Well it's 93.016 BILLION Light years. Yup it would take that many years to travel from one edge to the other. So you can imagine how helpful this light year is.
So let's have a look of some of the distances in lightyears.
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