Dark data is all the information your company collects but never uses, often...

https://stateofseo.com/what-does-agentless-really-mean-for-storage-analytics-tools/

Dark data is all the information your company collects but never uses, often hidden in files, emails, or backups. It can be 60-80% of your stored data, quietly taking up space and costing you around $2.5 million a year in wasted storage and management