The section of instruments that uses abbreviations of small symbols or pictures as well as letters is typically referred to as "notation" in the context of music. Specifically, this can apply to various forms of music notation, where composers use a combination of standard musical symbols (like notes and rests) along with abbreviations for dynamics, articulations, and other performance techniques.
In different fields, such as engineering and design, similar concepts can be found in the use of "schematic diagrams" which utilize symbols and abbreviations to represent components and their functions.
In both contexts, these notations help convey complex information in a format that is easier to read and understand. If you have a specific field in mind, please provide more details for a more precise answer.