What are the pieces of text that provide information on parts within an assembly called?

The correct choice refers to annotations, which are elements placed within a drawing or model to convey information about specific features or components. In the context of assemblies, annotations serve to clarify the purpose and dimensions of various parts, making them essential for communication and understanding in technical drawings.

Annotations typically include details such as part numbers, dimensions, and other relevant specifications, ensuring that anyone reviewing the assembly can easily identify and understand the characteristics of each component. This helps streamline the manufacturing process and reduces the potential for misunderstandings.

While labels and notes may also provide information, they tend to be used in different contexts. Labels are often used for identifying objects in a more general sense, and notes can provide additional commentary or instructions. Descriptions might outline the general purpose of an assembly but do not usually delve into the specifics of individual parts in the same structured manner as annotations. Hence, annotations are the most fitting term for the contextual need described in the question.