It’s not practical and sometimes not even legal to carry a weapon. What is a weapon? A weapon is a specialized tool for projecting force. It serves no other practical purpose than extending force from one body to another. The handgun is a perfect example. Handguns are designed to do one thing - extend force outward, to another human. Yes, a human. Guns and knives are considered deadly weapons. (Note - the EDC Krav Maga Self Defense Keychain is an improvised weapon - more on that later)
These are the three metaphoric pillars of self defense training: 1.) to know what to do, 2.) to be able to do it, 3.) to know how to do it. Shortchange and neglect the development of just one pillar, and the whole structure is going to have problems. If you are serious about self defense training, you've got to commit to all three.
When asking what is Krav Maga, people are really wanting to know what is different about the system than everything else. The problem with self-defense techniques is that they are often the starting point in problem solving, rather than the result of correctly applying principles. Krav Maga is advertised as being a principle and drill-driven system, but some instructors and groups do a better job of keeping training in line with advertising than others.
There is a big problem with the subject of violence in self-defense training and self defense techniques. Many instructors start first with self-defense technique, rather than starting with what violence really looks like. The problem is that most people are using the same words - Violence, and Fighting - but are describing different things.