Encryption is the process of converting data into a scrambled, unreadable form, known as ciphertext, in order to protect it from unauthorized access. The process of converting the data back into its original, readable form is known as decryption. 

Encryption is typically performed using an algorithm, or mathematical formula, and a secret key. In order to maintain the security of the encrypted data, the key is used to control the encryption and decryption process. There are different types of encryption algorithms, including symmetric-key algorithms (which use the same key for encryption and decryption) and asymmetric-key algorithms (which use a public key for encryption and a private key for decryption). 

Encryption is used to protect data in a variety of contexts, including when it is transmitted over networks, stored on devices or servers, or shared with other people. It is an important aspect of overall cybersecurity and can help to prevent the unauthorized access or misuse of sensitive or confidential information.