Question

What are catridges and what are they made up of

Answer 1

I guess you are referring to the cartridge used in a gun...

Some people call rifle cartridges "bullets," but in reality the bul­let is just part of the cartridge. A rifle cartridge is a case that contains primer, gunpowder and a bullet at the tip. The primer's job is to ignite the gunpowder, which in turn propels the bullet down the rifle's barrel and out to your target. The casing of the cartridge stays behind -- depending on the rifle you're using, you'll have to expel the spent cartridge manually or the gun will do so automatically.

In general, cartridge manufacturers name their product by bullet caliber -- the diameter of the bullet.