A cartridge, also called a round, a shell or ammunition packages a bullet, propellant (usually either smokeless powder or blackpowder) and a primer within a metallic, paper, or plastic casing that is precisely made to fit within the firing chamber of a firearm. The primer is a small charge of an impact-sensitive or electric-sensitive chemical mixture that can be located at the center of the case head (centerfire ammunition), inside a rim (Rimfire ammunition), or in a projection such as in a pinfire or teat-fire cartridge. Military and commercial producers also make Caseless ammunition. A cartridge without a bullet is called a blank. One that is completely inert (contains no active primer and no propellant) is called a dummy.
In popular use, the term "bullet" is often misused to refer to a complete cartridge.
Read more about Cartridge (firearms): Design, History, Nomenclature, Centerfire, Rimfire, Semi-automatic Vs. Revolver Cartridges, Bullet Design Types, Common Cartridges, Reloading, Caseless Ammunition, Trounds, Blank Ammunition, Drill Rounds