The wallet itself (i.e. its private key and public address) are created and stored on your Ledger device.
When the device is connected, Guarda can interact with the hardware wallet, allowing you to take advantage of all of Guarda’s functionalities (checking the balance and transaction history, sending, exchanging, and purchase of funds). As soon as the device is disconnected, you will no longer be able to perform any operations, as the access to the wallet’s private key will be removed.
However, your Guarda backup will continue storing your Ledger wallets, and you will be able to passively check your balance without having to reconnect the device every time.
In summary, though Guarda does not store your Ledger wallets, it stores information about them. Upon connecting the device, Guarda acts as an interface for you to interact with your Ledger wallets and manage your assets.