What gets fired from a rifle? Even a child could answer this question: a bullet. Now, what do you load into a gun? This one is a trick question, and anyone who answers “a bullet” has given themself away as a novice. The correct answer is a cartridge — which contains a bullet, yes, but also consists of other components. Without a proper propellant, a sufficient primer, a solid rim, or a good case to hold it all together, the only thing that would happen when you pull a trigger is a click sound.
Understanding the anatomy of a cartridge is great for preventing yourself from loading up with duds, dummies, or squibs. Of course, that knowledge is the bare basics. If you really want to improve your shooting, you should know how to pick the best cartridges for your rifle. Here is some information on the top-tier manufacturer Lapua and their excellent brass cartridges.