Japanese blacksmiths and knife makers use a wide variety of steels that can be broken down into two main groups: stainless steel and high-carbon steel. Stainless steel is easier to care for and will always have a nice clean look, while carbon steel can rust, but will develop a beautiful patina with care, like a broken-in leather jacket.
In terms of edge retention, you'll find both stainless and carbon steel knives can exceed most people's expectations.
For most knife buyers this page isn't a great place to start, but for those looking for that particular steel, we got you covered here.
We have a bunch of articles and resources for learning more about the steel in your knife and how to look after it. As well as some general guides if you are new to all of this to get you started. You can find tons more information here at our blog as well.