Bip39 Seed Phrase. The passphrase is just not selected with the predefined list of 2048 words – it could be any word or phrase you choose. BIP39 specifies a list of 2048 words from which the mnemonic phrase is decided on. Every word signifies a selection within a binary sequence, https://bookmarkingalpha.com/story19509717/bip39-passphrase-https-linktr-ee-bip39-bip39-wallets-things-to-know-before-you-buy