Users want to know what happens to their data when it's captured by the system.
The system communicates to the user what data it’s capturing, how that data is stored, how long it's stored for, and what other systems the data is being communicated to.
This is especially important when it comes to data captured based on user behaviour rather than explicit input. Ideally the system captures the least amount of data to achieve its task and stores it for no longer than is necessary, but sometimes data needs to be retained (e.g. for that user to maintain a profile or to train the system—or in some cases, another system—in general). In these cases, a key aspect of transparency is understanding the mechanics of this data capture and storage.