Handgun calibers refer to the diameter of the bullet and the cartridge used in handguns. Common calibers include .22 LR, .9mm, and .45 ACP. Each caliber has different characteristics, such as recoil, stopping power, and range, making them suitable for various purposes like self-defense, target shooting, or law enforcement. The choice of caliber can affect the performance of a handgun. For instance, .9mm is popular for its balance of size and power, while .45 ACP is known for its larger bullet and stopping power. Understanding these differences helps shooters select the right handgun for their needs.