A cryptographic key is a piece of information used in encryption and decryption processes to secure data. It acts like a secret code that allows only authorized users to access or modify information. For example, when you send a message using a secure app, a cryptographic key ensures that only the intended recipient can read it, keeping your communication private. There are different types of cryptographic keys, such as symmetric keys and asymmetric keys. A symmetric key is the same for both the sender and receiver, while an asymmetric key uses a pair of keys: a public key for encryption and a private key for decryption.