Seed phrase
Also known as: recovery phrase, mnemonic phrase
A list of words that backs up a wallet and can regenerate its private keys; it must be kept secret and offline.
Definition
A seed phrase (recovery phrase) is a human-readable list of words, usually 12 or 24, from which a wallet derives all its private keys. It is the master backup: anyone with it can restore the wallet and take the funds. It should never be entered into websites or shared with tools. For tax purposes it is irrelevant to share — you only ever provide public addresses or read-only keys.
Example
You write your 24-word seed phrase on paper and store it offline; you never type it into a tax app, which only needs your public address.