A parsec is 3.2 light years, about 19 trillion miles, or the distance to an object whose parallax angle in relation to Earth’s orbit is one arcsecond. Astronomers find it a useful measure, and it has a cool sound, don’t you think? I realize this explanation is sketchy, but here’s a diagram, and more details are readily available online for those whose desires tend that way.
The image was created by Srain at English Wikipedia – an altered version of :Image:Stellarparallax2.svg, which is an SVG version of :Image:Stellarparallax2.png. Stellarparallax2.svg was released into the public domain by its creator, Booyabazooka., Public Domain, https://commons.wikimedia.org/w/index.php?curid=4196613.