Wallet App app
The Digital Green Certificates Wallet App provides a user interface to store and manage personal DGCs directly on the phone. DGCs will be imported by scanning a base45-encoded QR code and decoding CBOR to JSON. Afterwards, it is symmetrically encrypted in the app’s sandbox and the symmetric key is stored in the system’s keychain. Multiple DGCs can be stored in the app. Access to the app is controlled via biometric data (e. g., Touch ID or Face ID). The wallet app can display any imported DGC as QR code for scanning and verifying with the verifier app.
Details on the Digital Green Certificate itself can be found at the corresponding web page by the EU Commission. Quoting from there:
A Digital Green Certificate is a digital proof that a person has been vaccinated against COVID-19, has recovered from COVID-19 or has a test result. The Digital Green Certificate is therefore a name used to collectively refer to 3 types of certificates: vaccination, recovery, test.