Artillery was a class of gun that was greater in range and firepower than a firearm. It could be employed as a ground based weapon, or onboard a starship. Archaic examples of these weapons used projectiles and chemical explosives. By the 22nd century projectile weapons were extinct, and had been replaced by particle beam weapon artillery.
History
Early artillery consisted of archaic types of gun first developed in Asia, using chemical explosives to propel a metal or stone projectile across a battlefield, into enemy infantry, castle walls or at ships. Later, the explosive shell was developed, which fractured sending deadly shrapnel in all directions upon impact. The majority of casualties in Earth's World War Two were caused by artillery. In 2364, the USS Enterprise was drawn into a simulated battlefield by Q. During this encounter, Q recreated several cannons from the Napoleonic Wars on ancient Earth. (TNG episode & novelization: Hide and Q)
When Captain Christopher Pike and the USS Enterprise encountered the Talosian civilization of planet Talos IV, the crew of the ship employed a ground-based artillery laser cannon in order to try to break through the Talosians defences. Later it was revealed that the cannon had devastated the seemingly impervious door, and it's untouched appearance was merely an illusion created by the Talosians telepathic powers. (TOS episode & novelization: The Cage)
During an invasion of the planet Cestus III in 2267 by the Gorn Hegemony, Captain James T. Kirk, who was Christopher Pike's successor as captain of the Enterprise, was forced to use a Starfleet issue mortar to bombard the enemy's position with photon grenades. (TOS episode & novelization: Arena)
Later in the same five year mission, the USS Enterprise visited the Smithsonian Annex on planet Nova Atar III. There the crew observed an old model B17 phaser cannon, nicknamed "The Real Equalizer", described as having been taken from the Federation's frontier near Nellapoor. The phaser was a ground-based weapon. The weapon was capable of being charged from a wide variety of power sources, giving it flexibility. Chief Engineer Montgomery Scott was able to salvage two functioning capacitors from the weapon. (TOS video game: Judgment Rites)
During the USS Enterprise-D's mission to stop Dr Tolian Soran from destroying the Galorndon Core star, Commander William T. Riker used a ground-based Romulan disruptor emplacement to destroy a Romulan Scout Ship. (TNG video game: Generations)
Artillery was also mounted on starships, serving as their main weapons systems, although they were rarely referred to as artillery, instead usually being addressed by their specific class of weapon such as phaser or photon torpedo. The weapons were used in conjunction to deplete the shields of an enemy vessel, then inflict direct thermal or kinetic damage on their hull. In the 22nd century, United Earth Starfleet employed a plasma cannon on their starships, but this was considered obsolete, being replaced by phase cannon weaponry, an early particle beam weapon in the phaser family. (ENT episode & novelization: Shockwave)