Seed Phrase
12 or 24 words backing up a crypto wallet.
Seed phrase = MASTER KEY. Anyone with it controls all your crypto. BIP39 standard: 12 or 24 words from 2048 list. Recovers wallet on any device (MetaMask, Ledger interoperable). NEVER online, NEVER photo, NEVER send. Write on paper (or steel: Cryptosteel), hide 2 physical places.
In plain words
12 or 24 English words that back up your entire wallet. Anyone who knows them controls all your crypto. Lose them = lose your crypto forever, there's no 'password recovery'. Write on paper (or a steel plate) and hide in 2 physical locations. NEVER online, photo, or cloud.
Example
Example seed (NEVER use!): 'apple banana cherry dog elephant frog grape happy ice juice king lemon'. Write on 2 papers in 2 locations. Better: steel plate (Cryptosteel, $80) fire/water proof. NEVER: text file, email, photo, cloud.
Also known as: seed, mnemonic, fraza mnemoniczna, recovery phrase