If you’re asking about the astronomical unit used for measurement Kiloparsecs are usually used.
The term parsec is derived from PARallax and arcSECond. A parsec is the distance at which one astronomical unit(distance from earth to sun) subtends an angle of one arcsecond. An arcsecond is ##1/60## of a degree or ##1/(21600)## of a circle.
Essentially it is the distance at which the movement of the distance of to the earth is perceived as a shift only ##1/60## of a degree across the sky. To put this into perspective one parsec is 3.26 light years 31 trillion kilometers or 19 trillion miles. A kiloparsec is simply 1000 parsecs.
Another thing used is a light year. It’s the distance light travels in 1 year. And that’s a lot. ! light year is just under 9500000000000 kilometers.