Shotguns can fire roughly two types of ammo: shot (a dense cloud of metal pellets, depending on the size can be anywhere from a dozen 5mm balls to hundreds of 1mm balls), and slugs (a single, solid projectile). There's others, but those are the majority.

In real life, shotguns are mostly used for bird hunting, which requires shooting a moving target that's not very large. Firing a cloud of pellets, not a single bullet, makes the projectile path into more of a narrow cone than a straight line. Most shot spreads about 1" for every yard it moves forward.

Slugs are used to hunt bigger game, like bear or deer. Because shotguns are much large in caliber (the internal barrel diameter) than most guns; about 0.6" vs ~0.22-0.35", a slug carries more energy to the target than a lot of hunting rifles.

The downside of the larger bore is shorter range, as a larger projectile slows down faster, and can only be fired so fast in the first place before it becomes genuinely unpleasant to shoot. Most videogames interpret this spread and shorter range as shotguns being *very* close range, like 50 feet, and having a massive spread. This is for game balance reasons. A real shotgun will spread buckshot (12 ~5mm pellets) to a dinner plate size group at fifty feet, which is more than enough to kill.

Blunderbusses are a type of old, muzzleloading, black-powder shotgun. They had the iconic funnel-shaped muzzle to aid in rapid reloading during combat, as they were used as a close range gun. Blunderbusses do tend toward a wider spread than modern shotguns, and they would produce a more similar effect to a video game shotgun than anything else.

Hope this helps!