The export creates a CSV file that contains all your data stored at pageplanr (but not the images you've uploaded).
You can use this file as a backup, for example. Not that this is necessary, because we at pageplanr save all your data multiple times. But if you decide to delete your account completely, you could create a new account at a later date and we would be able to restore your old data with the export file.
However, the export file also serves to give you the opportunity to view the data stored by us in accordance with the DSGVO.