Star Destroyer was a term used to describe a certain type of capital ship used by the Galactic Empire,
The term originated with the idea of a warship powerful enough to destroy entire star systems.
The Imperial-class was produced in large numbers and was the premier warship class of the Galactic Empire. All known variants were 1,600 meters long (one mile).
The Imperial I-class Star Destroyer possessed a main battery of six heavy turbolasers and two heavy ion cannons, arranged in four dual mounts flanking the ship's tower structure.