Cannon Designs

The early cannon designs were a vase-like shape made out of cast iron. "A smoothbore weapon is one which has a barrel without rifling" - Wikipedia. All cannons are smoothbore, so the projectile can come out more effeciently. Also, the first cannons were muzzle-loaded, which means they were loaded from the front of the barrel, not the back.
A howitzer is a type of artillery that has a short barrel and the use of small propellant charges to propel projectiles at high trajectories, with a steep angle of descent.
A mortar is a cannon that fires indirectly that fires shells at low velocities, short ranges, and high-arcing ballistic trajectories. It is typically muzzle-loading and has a barrel length less than 15 times its caliber.
The type of amuuntion today are high explosive, illuminate, white phosphorus, and armor piercing.