All blockchain wallets are cryptographically encoded, and have both public and private keys associated with them. Private keys are often referred to as a “secret key”.
As the names suggest, public keys are visible to all and used to identify wallets. However, private keys are what are used to decrypt the wallets – hence these are the critically important aspect. It is not possible to generate your private key from a public key for obvious security reasons.
Whoever is in possession of the private keys, essentially has control of the wallet and any funds that are contained inside. With Bitcoin wallets and many other cryptocurrencies, such as Ethereum based tokens, a private key is a 256-bit number. The format that the key is usually displayed in however, is a hexadecimal alphanumeric phrase.