The Composite Beam Superlaser was a type of superlaser.
The superlaser fired powerful proton beams. These beams could destroy a planet's core, rendering a target world uninhabitable. The weapon system required the dish to be manually moved out of locked position to the Death Star to fire, via a mechanical arm at the back of the dish.
The Concave Dish Composite Beam Superlaser was a more powerful version of this superweapon and was the actual design used for the Death Star I's laser.
The Composite Beam Superlaser was a proposed weapons system for the then-in-development Death Star I as an alternative in case the proposed Concave Dish Composite Beam Superlaser, at the time undergoing technical difficulties during its development, could not be developed. It would have been placed near the south pole. However, after the engineers for the development of the Concave Dish variant managed resolve the technical difficulties on the weapon, the Composite Beam Superlaser plans were scrapped.