Anonymisation
Short definition
Anonymisation is the process of irreversibly transforming personal data so that the person they relate to can no longer be identified by any means reasonably likely to be used.
In plain language
Truly anonymous data fall outside the scope of the GDPR (Recital 26). But anonymising is hard: removing the name is not enough if age, town and diagnosis together allow someone to be recognised. Aggregate statistics, such as the number of sessions run on a device in a month, are an example of information that does not normally identify anyone.