An ancient and historic weapon, a sword is, basically, a long knife. Composed of three parts, swords comprise a 'handle' (commonly called a hilt or haft), a protective crosspiece/guard and a really sharp blade. It's one of the simplest weapons ever made.
There are two basic styles of sword: European and Asian. Most European swords fall into one of three catagories. The simplest and crudest shortsword/broadswords came first. Around the 12th Century a new type of sword emerged. The longsword1 was bigger, heavier, and, thanks to the phenomenon of leverage, was capable of cutting armour like cheap aluminium. During the Renaissance era a third type of sword came into fashion: the rapier. Smaller, lighter, and more fashionable than previous swords, its deceptive slimness belied a remarkable strength.
Asian swords are much harder to classify. The nodachi was an enormous, lengthy, almost absurdly curved blade used to shatter armour plate. The naginata was a short sword blade mounted on a short quarterstaff.
Most famous of all Asian swords is the katana. Possibly the greatest and most romanticized of all swords, it is difficult to discern katana myth from katana legend. We know the katana was extremely sharp and sturdy. We know that it was not folded 2000 times2 as is sometimes proclaimed. A few other inaccurate legends attributed to katanas concern its abilities to cut through silk handkerchiefs when simply laid across the blade, to slice through stone, and to split a candle flame.
How to Make a Sword
Well, originally, you just took a pointy piece of metal, heated it up in a forge and hit it with a hammer. This did not work very well as the swords tended to bend and break, often in really spectacular, life-threatening ways. By about the Viking era, someone hit upon the idea of making swords in interlocking pieces, sort of like a jigsaw puzzle. Then someone came up with the idea of welding different length iron rods together.
Katanas are made in an entirely different way, in which a steel sheet is folded and refolded at least a dozen times. This results in an inordinately strong, sharp, and long lasting blade. The only drawbacks are the blade will necessarily have a triagonal cross-section, and it takes a lot of time and effort.
There is a great debate over the identity of the greatest swordmaker of all time, but the names Masamune and Murusame always come up. In modern times there is little competition for the title of greatest contemporary swordmaker. Fulvio Del Tin has been producing stunning, working replicas of European swords since the 1970s.
Buying a stainless steel sword is tricky at best. The lower carbon content in the steel means it will never hold a sharp edge for long, and it will be liable to bend at odd moments. However, low chrome alloy steels can be made that are suitable for swords. One of the main objections to using stainless steel for Japanese-style swords is that the grain of the metal (hada) cannot be reproduced because different techniques of working the metal are used; the etching of the grain was always considered a very desirable feature.
Make sure it doesn't have a rat-tail tang. The tang is the part of the blade which fits into the hilt. Rat-tail tangs are extremely thin, and inherently weak.
Don't hit anyone with your sword. The police are notoriously unsympathetic on this point.