Mnemonic phrase, mnemonic seed, or seed phrase are defined as a secret group of words that represent a wallet. When used in sequence they allow access to the cryptocurrencies stored within.
“Mnemonic” just means a memory aid such as rhymes, abbreviations and songs that help you remember something else. A mnemonic phrase is a group words, often 12 or more, created when a new wallet is made to store your cryptocurrency.
If the computer running your crypto wallet died, was lost or even stolen, you could use your mnemonic phrase to recover your wallet and crypto.
