A secret key (a string of numbers and letters) that can be used to encrypt or decrypt data and consequently prove ownership of assets on a blockchain.
A blockchain address or wallet is essentially a derivation from a public key that can be used as an identifier to send and receive coins and tokens. However, the owner of a blockchain wallet requires a private or secret key to sign transactions and cryptographically prove ownership.
Private keys are highly sensitive since anyone in possession of one can exercise ownership for the corresponding public address, moving assets out irretrievably.
If an individual loses their private key, they also lose access to their assets, since a private key cannot be regenerated from a public address.
