The Long Range Artillery is an indirect-fire structure used by the UEF and the Cybran Nation. It fires shells at targets within a wide area. It has extreme shot inaccuracy, but is effective at dealing damage to (unshielded) bases and harrassing Illuminate bases.
On maps like Seton's Clutch and Iskellian Coast, if you are about to be nuked in a 4v4 game, drop your commander and a couple engineers with fighter guards on the side islands. Long Range Artillery is key to this strategy as it allows you to safely destroy unshielded targets from your island base.
If you're UEF, spend the extra points researching the Disruptor station. For roughly the same price, you get almost double the DPS plus shots are fired in 4-shell bursts which are more likely to shut down and penetrate a shield.
In order to penetrate heavily shielded bases, you will need many of these.
Like SC1, the Cybran version is cheaper than the UEF's.
Long range artillery have the same structure veterancy rates as point defences, which means that if they take out a number of tanks/mass extractors they will gain veterancy very quickly, giving them a substantial 50% damage boost at the highest veterancy level.
The cybran long range artillery can benefit from the 30% increased firing speed from the Rate of Fire research. This increases the long range artillery firing speed to once every 3.5 seconds (0.5 seconds faster firing than the UEF artillery.)
In the Infinite Battle Pack DLC, the Cybran can research shell camera and the Cybran Artillery can essentially peek in to an enemy base. When a shell strikes its target, line of sight is briefly enabled from where the shell landed.
UEF artillery benefits from a researchable increased range bonus, making it favored by most players over the Cybran artillery which in turn deals much more damage in terms of DPS than the UEF artillery
The long range does, however, have one notable "advantage". It fires much faster than the Disruptor Station and you can put a few more shells into your target. Although it's best to use this in conjunction with the Disruptor Station as the Disruptor takes out shields and the artillery to leave important strucures exposed.