In Simple Words
If your phone or hardware wallet is lost or damaged, your bitcoin do not disappear from the Bitcoin network.
What matters is being able to recover the keys that control your bitcoin. Many self-custody wallets use a recovery phrase, commonly 12 or 24 words, for this purpose.
Those words are more than an app password. They can help recreate your keys in a compatible wallet, provided the backup and any extra settings, such as a passphrase, are correct.
Avoid screenshots, photos, cloud notes and messages containing your recovery phrase. Record it using the wallet’s recommended method and store it privately, protected against both theft and loss.
Never enter your recovery words into a website or share them with anyone claiming to be technical support. Your recovery phrase is a backup for control of your bitcoin, not information to give away.