Family of steels designed to machine other steels. Major difference is thatthese tools will hold an edge even when heated red hot by friction. While this is less likely to happen to your knife in everyday use some of these steels have very high wear resistance. M2 for example. Though high speed tools are rather brittle, thus not appropriate for large blades.
Is a term used to describe a wide range of steel alloys used for cutting tools. These materials incorporate varying amounts of many different elements (Tungsten, Molybdenum. Cobalt, etc.) to produce specific hardness and cutting characteristics. High Speed Steel tools are more resilient than those made from carbide, however they do not possess the hardness or abrasion resistance.