A Rocket Assisted Projectile is an artillery

Artillery

Originally applied to any group of infantry primarily armed with projectile weapons, artillery has over time become limited in meaning to refer only to those engines of war that operate by projection of munitions far beyond the range of effect of personal weapons...

 or cannon

Cannon

A cannon is any piece of artillery that uses gunpowder or other usually explosive-based propellents to launch a projectile. Cannon vary in caliber, range, mobility, rate of fire, angle of fire, and firepower; different forms of cannon combine and balance these attributes in varying degrees,...

 round incorporating a rocket

Rocket

A rocket is a missile, spacecraft, aircraft or other vehicle which obtains thrust from a rocket engine. In all rockets, the exhaust is formed entirely from propellants carried within the rocket before use. Rocket engines work by action and reaction...

 motor for independent propulsion. This grants the projectile both greater speed and range than an ordinary shell, which is propelled only by the ballistic

Ballistics

Ballistics is the science of mechanics that deals with the flight, behavior, and effects of projectiles, especially bullets, gravity bombs, rockets, or the like; the science or art of designing and accelerating projectiles so as to achieve a desired performance.A ballistic body is a body which is...

 force of the gun's exploding charge. Some forms of Rocket Assisted Projectiles can be outfitted with a laser-guide for greater accuracy.

When NATO standards required member armies to have corps-level artillery that could fire to a maximum range of 30,000 m (18.6 miles), nearly all member nations solved the problem with RAP rounds in their 155 mm (6.1 inch) artillery.