Dark data is the vast amount of information companies collect but never use —...

https://www.sierrabookmarking.win/dark-data-is-all-the-info-your-company-stores-but-never-uses-think-emails-old

Dark data is the vast amount of information companies collect but never use — around 60-80% of it just sits inactive. This unused data takes up storage, slows down systems, and can cost businesses an average of $2.5 million each year