Dark data is all the information your company stores but never uses—think of it...

https://hotel-wiki.win/index.php/Komprise_Analysis_vs_Other_File_Analytics_Tools:_What_Sets_It_Apart%3F

Dark data is all the information your company stores but never uses—think of it as digital clutter taking up space. Around 60%-80% of file data stays inactive, costing you money and creating security risks