It's an app, and data is submitted with a tap to approve. The data is just attribute / proof pairs (eg nationality:British / true), and the bundles assembled from these pairs will differ between use cases. Nightclub proof of age would just need the 'over 18' proof, while opening a bank account would need a photo, name, address, date of birth, nationality etc. In other words, there isn't a single Digital ID. The 'ID' is just a container for a specific use. They can be reused, but they will often be single purpose or generated from the attributes saved in your wallet the moment a service requests your data. The best way to think of this is that it gives you a way to pass on your citizen data with authority, and without having to overshare.