The subject of this work is high steels, their properties and applications. There are several groups of tool steels, however, this paper focuses on high speed steel, which falls into the category of highly alloyed tool steels. The introduction briefly defines what the tool is, presents its origin and further development of tool steels. The division of tools according to their operating temperatures and alloying degree is explained. This paper also describes and lists the requirements placed on the properties of tool materials (general properties, special properties and manufacturing properties). Furthermore, the impact of alloying elements on the tool itself, the division of alloying elements used to make the tool, as well as their properties are also presented. The paper further describes high-speed steels, i.e., their operating conditions, pseudo binary diagram, and metallographic properties. Moreover, the paper explains heat treatments high-speed steels are required to undergo with the aim of achieving certain properties and structures. Finally, basic principles of selecting high speed steels and examples of application of the steels are also presented.