I would advice you to use its html offline:
https://github.com/iancoleman/bip39/releases/latest/Click on that link, download the html and use a text editor to open it on an airgapped device. Do not use the online version, for safety reason.
What is most important is the seed phrase
You can recover your wallet with BIP32 extended private key which defines HD wallet. Your keys and addresses can be generated with the BIP32 extended public key.
With extended private key, you can also get access to all your keys and addresses pertaining to an address type. Which means different derivation path which are legacy (BIP 44), nested segwit (BIP49) and native segwit (BIP84) for the different extended private key
With extended public key, you can get access to all your addresses, but not your private keys, it can be used for watch-only wallets. Also different derivation path for the addresses which are legacy, nested segwit and native segwit.
For the extended private key and extended public key:
BIP44, legacy, the extended private key starts from xpri while the extended public key start from xpub, the address start from 1
BIP49, nested segwit, the extended private key starts from ypri while the extended public keystart from ypub, the address start from 3
BIP84, native segwit, the extended private key starts from zpri while the extended public key start from zpub, the address start from bc1q