so now i understand that the PASS PHRASE is only optional to create a HIDDEN WALLET:
https://wiki.trezor.io/Passphrasecorrect ?. does it serve any other purposed if my wallet is lost or stolen ?
Passphrase is only optional but I would highly recommend that everyone who owns Trezor wallet uses secure passphrase because it is not stored anywhere on device and it improves security for your device.
If you lose your device or your seed words, nobody will be able to take your funds if they don't have your unique secure passphrase, so keep it safe on separate place.