Carronades are built much lighter than cannons of equivalent caliber. This means that a much higher caliber carronade can be placed in a smaller cannons position. However the maximum amount of propellant used is much lower due to lighter construction. This leads to the ability to fire a larger projectile but at lower velocity and range. A ship carrying carronades will have to maintain close range to the enemy to apply damage. This can make carronades an attractive option for lighter ships that can properly dictate range while avoiding enemy broadsides.
Age of sail cannons and carronades are rated by caliber which is the weight of their round shot in imperial pounds. This is not to be confused with modern caliber which is categorized by the diameter of projectiles. Increasing caliber of cannon generally increases damage and range at the cost of loading time.