Ammunition is gunpowder and artillery, or broadly anything that can be used in combat including bombs, missiles, warheads, landmines, naval mines, and anti-personnel mines. The word comes from the French la munition which is all material used for war. The collective term for all types of ammunition is munitions.
The purpose of ammunition is to project force against a selected target. However, the nature of ammunition use also includes delivery or combat supporting munitions such aspyrotechnic or incendiary compounds. Since the design of the cartridge, the meaning has been transferred to the assembly of a projectile and its propellant in a single package.
The "packaged" components that are needed in order to fire in a case or shell holding a primer, (which produces the spark) a charge of propellant (gunpowder) and a projectile (bullets, slug or pellets.) Sometimes called "fixed ammunition" to differentiate from the individual components placed separately in muzzleloaders. A single unit of ammunition in modern firearms is called a cartridge. The units of measure for quantity of ammunition is rounds. There are hundreds of sizes of ammunition.
Diagram of Ammunition Round Handgun and Rifle Ammunition