If you want a practical example of psuedonymisation then consider a case where you have two internal systems that serve different purposes (say one is used as a

If you want a practical example of psuedonymisation then consider a case where you have two internal systems that serve different purposes (say one is used as a CRM, the other is used for business reporting). The CRM database is copied over to a separate database that the reporting system feeds from. Now in reality the reporting system (which will generally give you aggregated trend reporting) doesn't need a full copy of all production data as it only needs to utilise a limited subset of the overall data. So instead of the full copy of the CRM database being copied over to the reporting database, you filter the data so you only copy over an anonymised dataset. That is pseudonymisation in a nutshell. Because you still retain the separate dataset in your system, the data is not truly anonymised, so is said to be pseudonymised. Overall I see it as linked to the requirement for data minimisation. Any particular system should only have access to the data it needs to perform its role.