This is one of those topics where you will get a multitude of answers to the question “What is the best knife steel?”. There are typically 3 types of steel used for knives and other cutting tools (axes, machettes):
Tool Steel – Typically D2, O1. These are generally hard steel alloys used in cutting tools. Tool steel is carbon steel alloyed to make steel with properties particularly suited to make tooling tools such as cutting tools and dies. They are distinctly hard, with abrasion and deformation resistance. They also tend to hold a very sharp edge for a longer period and are still reasonably easy to field sharpen. These are alloyed with different elements to attain specific properties and are generally more expensive than carbon steel. This type of steel is also not stainless and will corrode if not maintained.
Carbon Steel – typically 1095 and 5160 for swords. These knives are usually tough and durable. They are easy to field sharpen, which is important for camping and survival knives, and take a sharp edge. Typically used for camping and survival knives, axes and machettes. The down side is that these knives are not corrosion resistant and need care. These blades and also blades made from tool steel will form a “patina” (grey mottled pattern)over time. Many knife collectors find this to be an aesthetic of the knife as no two knives will form the same patina. This patina also protects the steel to some extent. These are the most cost effective steels.
Stainless Steel – basically carbon steel with added chromium to resist corrosion. They are also alloyed to attain more specific properties. These are more difficult to work with and cost considerably more than the other two types. A high grade stainless steel is needed to make a blade comparable in hardness and toughness to carbon or tool steel
Non ferrous metals – such as brass, bronze, pewter, silver, aluminium. These metals are used as parts of the handle, (butt, bolster, guard etc) mostly for decoration and aesthetics.
In each of these categories you will of course also have a range of properties depending on the steel, for example even though D2 and O1 are both tool steels, their properties are quite different. O1 will sharpen a lot easier than D2, but D2 will keep its edge longer. D2 is also semi stainless with a high chrome content.