A cartridge is also called a round (or a shell), and it is used to package a bullet. Caseless ammunition can also be produced by military and commercial producers. A empty cartridge does not contain a bullet. A dummy contains inert, which means it has no active primer or propellant.Popular usage of the term bullet often misunderstands it to mean a complete cartridge.
The cartridge case seals the firing box in all directions, except the bore. The primer compound is ignited when a firingpin strikes it. The primer compound does not explode. It deflagrates which is a rapid burning gas. The propellant ignites when a jet of gas is released from the primer.
The burning powder gasses pressurize the case and expand it to seal it against its chamber wall. These propellant gasses push on the bullet’s base. The bullet will respond to this pressure by moving down the bore of the barrel . The chamber pressure drops below atmospheric pressure after the bullet leaves a barrel. The chamber pressure causes the case to contract slightly, after being elastically expanded. This makes it easier to remove the case from its chamber.
Brass is a popular case material. It is resistant to corrosion. Brass case heads can be work-hardened to resist the high pressures of cartridges. This allows manipulation via extraction and ejection with minimal damage to the metal. It is easy to anneal the neck or body of a brass case to make it strong enough to allow for reforming, so that it can easily be reloaded multiple times.
Steel can be used in “plinking”, as well as some military ammunition (mainly the former Soviet Union or China). While steel is more affordable than brass, it’s not possible to reload and reuse steel containers. Most military forces consider small arms cartridges disposable, one-time use devices. But, the case weight (or mass), affects how many rounds a soldier can carry. So lighter steel cases are an advantage for military purposes. However, steel is more vulnerable to corrosion and damage, so all such cases must be varnished or sealed against the elements.
A downside to these cases, which have a higher strength than the annealed necks for brass cases, is that propellant gas can blow back into the chamber. The chamber wall is relatively cold and the gases that are contained in them condense. It can be difficult to extract the fired cases due to this solid propellant residue. This is not a problem with small arms of former Warsaw Pact states, as they were built with larger chamber tolerances that NATO weapons.
CCI has aluminum cased cartridges. These cannot be reloaded due to aluminum fatigues which can be easily reloaded during firing or resizing. To discourage reloaders who try to reuse these cases, some calibers use non-standard primer sizes.
As detailed below, paper was used in early cartridges.
Specifications for cartridges include neck size, bullet length, caliber maximum pressure, header , maximum force, headspace overall length, case body width and taper, shoulder design and rim, among others. Most cartridge types have specific characteristics that are tightly controlled. They can’t be interchangeable. Although exceptions may exist, they are usually limited to cases in which a shorter cylindrical rimmed ammunition cartridge can be used within a longer chamber (e.g..22 Short chamber in the.22 Long Rifle chamber or.38 Special chamber in the.357 Magnum chamber). Centerfire prime type (Boxer, Berdan) can be used interchangeably, though not in the same situation. A deviation from any of these specifications may result in firearm damage or, in extreme circumstances, injury or even death. Also, the incorrect type of cartridge can cause gun damage or bodily injuries.
Multiple standards bodies determine the specifications of cartridges, including SAAMI in America and C.I.P. In many European countries. NATO also conducts its own tests of military cartridges in its member states; there are differences between testing methods and NATO cartridges may be unsafe when loaded into a weapon that is designed for a cartridge certified 
Bullet diameter can be measured as a fraction of an in (usually in 1/100, 1/1000, or millimetres). The length of cartridge cases can be measured in inches or millimetres.
The use of paper cartridges has been going on for as long as handguns. There are several sources that date their usage back to the late 14th Century. Historians have noted their use in 1586 by Christian I soldiers [not in the citation given], while the Dresden Museum[which] has evidence proving their use in 1591. Capo Bianco, a 1597 writer, stated that paper cartridges had been used for years by Neapolitan soldiers. They became popular in the 17th-century.  The 1586 cart contained a charge powder, and a bullet inside a tube. Because of its use in cartridges, thick papers are still called “cartridge-paper”.
This cartridge was used with muzzleloading military firearms.
Cartridges for integrated paper
In Paris, in 1808, Jean Samuel Pauly a Swiss gunsmith and Francois Prélat conceived the first fully integrated cartridge. Pauly was the inventor of the first fully-contained cartridges. Pauly created the first fully self-contained cartridges.  The cartridges were loaded through the breech and fired with a needle.
There is no other invention related to firearms that has brought about such fundamental changes in gun construction as the “expansive cart case.” It prevents gas from leaving the gun’s barrel when it is fired by using an expansive cartridge box with its own ignition. Prior to this invention, shotguns as well as sporting rifles were loaded using powder flasks along with shot bags, flasks, or bullets. French inventors created the pinfire cartridge.