The security model is that your keys are stored in an encrypted file that exists on your phone and also on an edge server. All you need is your username and password to download the wallet on a new device. As long as you use a good password your keys are safe.
More importantly you can export the private keys if you want to transfer them to a different wallet app or write them down.
It doesn't support seed phrases though, only raw keys.
It has the ability to export an xpub which is helpful if you're setting up an online shop and want to receive payments to it.
It's also one of the few wallet apps where you can sweep a private key from another wallet into your edge wallet. You can paste in the private key or scan a QR code and it will do an on chain tx to transfer the funds from that private key into your edge wallet.