Private Key / Seed Phrase
Plain English
Your master password - a set of 12-24 random words that control your crypto. Like the key to a safe, anyone with these words has complete access to your money. Never share it, never type it on websites, and keep it written down somewhere very safe offline.
Technical
The secret component of a cryptographic keypair that authorizes transactions and proves ownership. Seed phrases (BIP39 mnemonic) encode the private key in 12-24 human-readable words, allowing deterministic wallet recovery. Cryptographically signs transactions without revealing the key itself. Loss means permanent asset forfeiture - there's no recovery mechanism.