There are different kinds of blades, created by various forge techniques, but which have the only common aim : to get a blade enough hard to have a quite sharp and sturdy edge, and in the same time to have a blade enough tender to absorb the strokes without any breakage. Here is the paradox to reach for a good katana. So, to help you, here is a list of kind of blades ranked in accordance with their quality and rarity. It is explained how they are closed to the perfection.
The marus, carbon steel made (1045, 1060, 1095)

The carbon steel-made katana is the first grade. (note that "carbon steel" is funny to say as every one knows that steel contains carbon by definition) . Here we have rather efficient katanas, as you have to know that during the Second World War, for example, many katanas were marus. Carbon hardens metal, so we are speaking about maru 1045, 1060 or 1095 to say that we have 0,45% with carbon or 0,60 % or 095%. These ate the more common rates, although we find many 1055, 1070, 1075 or 1090.
The 1095 is the top of this range of katanas : enough carbon to be very efficient and perfectly sharpened, nevertheless staying supple enough to absorb the strokes.
A 1045 is no so efficient but being softer it assumes a better absorption of impacts. It costs something about 250 dollars.
A 1060 is about 300 dollars and a 1095 from 325 dollars… All prices are indicated to give you just an idea because they depend of the quality of the grip or of the sheath.
We also speak about : Shigane steel (tender steel 1040 to 1050), Kawagane steel (Hard steel 1055 to 1075) and Hagane steel (very hard steel 1080 to 1095).

Note that the rate of carbon also gives you information about a lot of elements, such as chrome or molybdenum. Chrome is used to avoid rust (steel is considered as stainless when over 13% chrome) and molybdenum is used to absorb the impacts without breakage despite a high carbon rate. And this explains why the 1095 is the best in this range of blades.

T10 or C105 steel

The T10 steel (commonly called C105 in Europe), is issued from a very interesting concept. Actually it contains about 1.05% carbon, permitting a harder edge and so it is more lasting than the 1095, and also it can be sharpened more accurately. But at the contrary of a classic steel, it has very particular additives which provide an excellent suppleness. Because of its hardness we would expect less suppleness and less resistance than for a 1095 when facing mighty impacts (not so good absorption of vibrations), but on the contrary the T10/C105 proved to be suppler. Consequently this steel gathers all the advantages and it is broadly used in the USA. Lately it has come in France, and we are glad to use the T10/C105, since year 2019, instead of 1095 for a better quality blades, our prices staying the same.
Attention : in Europe was already a well known German brand that presented this steel as "Tamahagane". Obviously it is not true, the T10/C105 is really a steel of a great quality, but the Tamahagane is made respecting a very special processing.

The Damas blades

The damas steel blades are created by mean of an ingenious process : several layers of tender and hard steel are successively stacked. So, we obtain a blade at the same time hard and supple. More, you get a blade with veins, a pleasure for your eyes. This picture doesn't need any comment, really you can see the different steel layers.
But you may find false damas blades. For example an industrial lamination can imitate the damas aspect, and it is so that even some well known manufacturers are using this technique. In this case there is Mcusta, the well-known Japanese forge and its famous knives (but this imitation, the knives are of a very good quality). It is not easy to detect these imitations, so don't be surprised to see some "damas katanas" at a very low price ! It is common … and now you know why. The cost of a real damas katana is something about 400-500 Dollars.

The composite katanas

As said by its name this range of katanas consist to forge the blades with several kinds of steel, arranged in order to have a hard edge and a soft core to improve the elasticity. Clearly it is with this kind of katanas that we find some master pieces, with blades which are at the same time hard, efficient and resistant.

This scheme shows the different kind of composite katanas with, as you have guessed, a hard steel in blue, a medium-hard in light blue and tender in grey.
Katanas made with Tamahagane steel

The Tamahagane steel is the traditional Japanese steel which was used to forge the blades. It is a steel with a high carbon rate (sometimes up to 1.5%) that lead to create sabers extremely sharp. It is usual to distinguish the tamahagane issued from Japon and others. In any cases, the ferruginous sand is important. It must contain much molybdenum and on the contrary very few phosphor (which has an opposite effect and gives a less supple steel). Obviously the result gives a steel of very high quality.