A japanese katana sword is an iconic symbol of japanese culture. It is one of the three sacred Shinto relics along with a bamboo bow and a halberd, all of which represent the myth of Susanoo, the god of thunder who killed the giant serpent Yamato-no-Orochi that terrorized his province of Izumo.
The katana is often regarded as the ultimate Japanese sword, a weapon that blends elegance, cutting power and durability. Its blade is usually made of steel and it is tempered by rapid cooling to achieve both its renowned sharpness and strength. A distinctive feature of a katana is the wavy line known as hamon that indicates a differential heat treatment process called yaki-ire, which involves heating and cooling the blade at different rates.
Another distinguishing feature is the curved tip of the blade, or kissaki. It is a slender, pointed end that is more pronounced on the tachi than on the later katana. It was designed to enable warriors to cut through the body of an enemy without having to bend or twist the sword to complete the cut.
The tachi was the main sword for warriors until around 1300 AD, when smiths began to produce the katana. The katana was a larger and more powerful sword that could be used in open field combat or in close quarters battles. It was favored by samurai, the military nobility who governed Japan until the arrival of the Mongol armies under Kublai Khan in 1274. More information here