I wish I owned one of these, a REAL one, that is. See, the ones sold online like at swords.com are spendy even for the cheaply made ones (nearly $300 for a "Japanese" sword made without any folding!!!). Alright, so you probably want to know what a 'real Japanese sword' is like.
A REAL Japanese sword begins as enough metal. It is quickly shaped into a sword, then the folding begins. The metal is hammered out to twice the width the sword would be, then folded in half in that direction. Then the halves are welded together and the process is started over again. This is not your standard arc-welding either; the metal is heated hot enough so that the contacting surfaces actually fuse together. I have heard that a twisting process is sometimes used as well (whenever the metal doubles in length, most likely).
When all is done, the sword has 224 layers (or more if more folds were made) to it (the welding process does not eliminate the layering). A well-made sword can take up to a year for a master sword maker to complete. This type of sword is so sharp that a falling piece of silk is cut completely in half upon landing on the upturned edge of this sword (no sword motion necessary).
In the game Nethack, the samurai character will do "twoweapon" combat with a katana and a wakizashi (four foot sword and two foot sword respectively).
From http://www.csse.monash.edu.au/cgi-bin/cgiwrap/jwb/wwwjdic?1E it seems that "katana" means a swift or sudden movement in Japanese.
From http://www.highlander.org/roleplaying/appendix.html, many immortals use katanas for their main weapon. The reason for this is that the sword is the "only efficient weapon" for decapitation. One of the swords listed here, wielded by Ramirez, is said to be over 2000 years old. (I have no accurate information yet as to when the Japanese began to use the folding process for the katana of real life).