The boxer primer, which was invented in Europe, is the most common priming type in America. You can look into an empty casing and see the single round flash hole that denotes the boxer system. Boxer primed ammo is (mostly) easily reloadable.
The Berdan primer, which was invented in America, is the most common priming system in Europe(Although the boxer sys. is being adopted by many ammo makers over there). You can look into a fired case and see the two tiny flash holes that are characteristic of the berdan system. Berdan primed ammo can be reloaded but it's a PITA to do so. Mostly the only people that bother are those who have exotic/old/rare weapons that they have berdan brass for and boxer brass isn't available or is very expensive.
Don in Ohio