The legacy name of the emirate-level authority that licenses mainland businesses. In Dubai, the DED was renamed the Department of Economy and Tourism (DET) in 2022. Other emirates still use DED (Abu Dhabi DED, Sharjah DED, Ajman DED).
Any mainland company set up in Dubai before 2022 will have 'DED' on old paperwork; new Dubai mainland licences now say 'DET'. Outside Dubai, the DED is still the authority you register with.