Okay, so imagine you are playing with your toy sword and it's a bit heavy. Japanese swords are like toy swords, but they are made by really skilled crafters who use special materials and techniques.
First, they use a type of iron that comes from a special place called the "tamahagane". It has impurities that are considered good for making swords. Then, they heat this iron until it melts and they pour it into a mold.
Once the iron has cooled, they take it out of the mold and it looks like a long bar of metal called a "tamahagane bloom". They then hammer this bar many times to make it flat and thinner. Every time they hammer it, they fold the metal over itself to make it strong. They do this many times, sometimes up to hundreds of times.
Next, they add another type of metal called "high-carbon steel" to the edge of the sword. This metal is super sharp and helps make the sword more effective in battle.
After that, they use a special tool called a "tanren-bo" to shape the sword. It's like a big file that scrapes away at the metal slowly over time. This takes a long time to do, sometimes even months!
Finally, they add a handle to the sword, called a "tsuka", made out of wood and wrapped in silk or leather. They also add a fancy guard called a "tsuba" to protect your hand.
So there you have it! A Japanese sword is a very special kind of toy sword that is made of really strong metal, takes a long time to make, and has a fancy handle and guard. They are not toys though, they are real weapons used in ancient Japan by skilled warriors called "samurai".