Flak cannons are anti-aircraft artillery designed to shoot down enemy aircraft. The term "flak" comes from the German word "Fliegerabwehrkanone," which means "aircraft defense cannon." These weapons fire explosive shells that detonate in the air, creating shrapnel to damage or destroy planes. Developed during World War I and widely used in World War II, flak cannons were crucial for protecting ground forces and strategic locations. They come in various calibers and can be mounted on vehicles or stationary platforms. Notable examples include the Bofors 40 mm and the German 88 mm flak gun.