A parsec is a unit of distance commonly used in astronomy. It is defined as "the distance at which the radius of the Earth's orbit subtends 1 arcsecond (1/3600 degrees)." It is equal to around 3.26 light years, 3.09×1016 metres or 1.92×1013 miles. The unit is normally denoted with a lower case "pc".
Parsecs, like light years, make the large distances encountered in astronomy much more manageable. For example, the distance to our nearest star, Alpha Centauri, is around 0.769 pc away and the Milky Way is around 30 kpc across.
- Parsec from britannica.com