Your Ryanair Wallet is where any refund you have requested and are entitled to in relation to a flight disruption is initially stored.
If your flight is cancelled and you request a refund, it will be deposited to your Ryanair Wallet within 24 hours. From here, you may use this refund to pay for future flights, or you can choose to withdraw it in one click and have it refunded to your original form of payment. You will be able to access your Ryanair Wallet when you log in to your myRyanair account.
See Ryanair Wallet T&Cs here.