No, they are different.
A rifled barrel is a solid bar of steel which has a hole drilled through it down the center. The hole is spiral cut with lands and grooves (called rifling) such that when the bullet is fired, the bullet contacts the lands and spins as it moves down the barrel. This spinning stabilizes the bullet to improve range and accuracy.
A Damascus barrel starts with a stack of many different kinds of steel bars. The stack is hammer welded (pounded to the point where the steel flows together) to make a flat sheet. The sheet is wrapped around a steel bar to form a shotgun barrel and hammer welded to make it complete. When new, Damascus barrels are beautiful with the many colors in the steel. They don't age well, though, and often will have subsurface corrosion which weakens them to the point where they shouldn't be fired, even with the proper black powder ammunition. They should NEVER be fired with smokeless powder ammunition.
a slug is normally use in a shot gun and they are not rifled a gun with a rifled barrel should shoot a Shell that is the same caliber as the gun.
Neither barrel is rifled.
Not safely
You look down the barrel and if it is swirled it is a rifled barrel and if it is not swirled it is a smooth bore
Shooting rifled slugs is the ONLY way to shoot thru a smoothbore for deer. If you shoot sabot slugs thru a smoothbore, it will not spin and therefore not be accurate. For accuracy, the slug must spin out of the barrel. Either shoot a rifled slug thru a smooth barrel, or shoot a saboted slug thru a rifled barrel.
The same size forearm is used on all barrel lengths of the 500.
All grooves are made at the same time with a tool called a "button" that is pushed or pulled down the barrel
Smooth-bore refers to a firearm or cannon which does not have a rifled barrel (a rifled barrel is one with ridges that corkscrew down the barrel to impart a spin to the bullet)
Slugs! If its rifled it is a deer hunting barrel.
The Benelli Supernova does not come with a damascus barrel as a factory option. However, some custom gunsmiths may offer aftermarket damascus barrel options for the Supernova.
Rifles and pistols
Assuming you mean a barrel that is for lead pellets, if the barrel is not rifled, steel shot will not damage the smooth barrel. If it is rifled however, steel shot will in fact damage the rifling.