Historically, artillery refers to any engine used for the discharge of projectiles during war. The term also describes ground-based troops with the primary function of manning such weapons.

The word as used in the current context originated in the Middle Ages. It comes from the Old French atellier meaning "to arrange", and attillement meaning "equipment". From the 13th century an artillier referred to a builder of any war equipment, and for the next 250 years the sense of the word "artillery" covered all forms of military weapons.

"Artillery" is a general term covering several varieties of large-calibre weapons; currently these fire an explosive shell or rocket and are of such a size and weight as to require a specialized mount for firing and transport. Weapons covered by this term in the modern era include "tube" artillery such as the howitzer, cannon, mortar, and field gun and "rocket" artillery. Older engines like the catapult, onager, trebuchet and ballista are also artillery but generally fired a solid shot.

The types of tube artillery are generally distinguished by their ballistic trajectory. Cannons (such as infantry support guns or the guns on a naval ship) are typically low-angle weapons designed for a direct-fire role. Mortars are high-angle weapons originally used to drop shells behind the walls of a city. Howitzers are capable of both high- and low-angle fire. They are most often employed in an indirect-fire role.

Types of artillery:

field artillery - mobile artillery used to support armies in the field. Includes:
- infantry support guns - directly support infantry units
- mountain guns - lightweight artillery that can be moved through difficult terrain
- mortarss - lightweight weapons that fire projectiles at an angle of over 45 degrees to the horizontal
naval artillery - cannons mounted on warships and used either against other ships or in support of ground forces.
coastal artillery - Fixed-position artillery dedicated to the defense of a particular location, usually a coast (e.g. the Atlantic Wall in WW 2) or harbor. Not needing to be mobile, coastal artillery could be much larger than equivalent field artillery pieces, giving them longer range and more destructive power. Since World War II, however, modern weapons and tactics have made them largely obsolete.
anti-aircraft artillery - artillery (usually mobile) that is dedicated to the ability to attack aircraft from the ground.

Depending on the calibre of the weapons, artillery is used in a variety of roles. Mortars fire relatively small-calibre projectiles in a high arc against targets concealed from the view of the firer. Other battlefield artillery battlefield includes longer-range weapons that fire in a flatter arc - the target may or may not be in view of the firer. Howitzers and such are generally used against hard targets such as bunkers or MBTss. Modern field artillery is often self-propelled (permanently mounted in a carriage or vehicle capable of moving independently) in order to move quickly from one firing position to another - to both support the fluid nature of modern combat and to avoid 'counter-battery fire'.

Radar has had a major impact on artillery. Coupled to computers it can accurately track an enemy shell in flight back to its firing point. This can be used as targeting information for 'counter-battery fire' - a term for the attack by artillery on an enemy artillery site. Radar improves the ability to return fire quickly and accurately. This greatly increases the all-weather flexibility of modern artillery. The rise in counter-battery capabilities drove the field artillery to adopt a 'shoot-and-scoot' philosophy emphasizing constant maneuver from place to place. This has required reliance on sometimes temperamental technology and increased the cost of modern field artillery pieces.