What do we call data that provides information about other data?

The term that designates data providing information about other data is "metadata." Metadata serves to describe various aspects of data sets, such as their content, quality, format, and structure, thus facilitating understanding, management, and usage of the data. For example, in a digital photo, metadata might include details like the camera settings, the date taken, and the location, all of which help in categorizing and retrieving the image later.

In contrast, the other terms do not fit the definition of describing data about data. Databases are structured collections of data. Primary keys refer to unique identifiers for records within a database, ensuring that each entry can be distinguished from the others. Data sets are collections of related data points organized for analysis but do not inherently describe the nature of that data themselves. Understanding metadata's role is crucial in managing and leveraging data effectively in various applications.