Final answer:
Encryption is the process by which data is converted into a non-readable format to secure it from unauthorized access, using an encryption key to transform the plaintext into ciphertext.
Step-by-step explanation:
The process of converting data into a format that cannot be read by another user is known as encryption. It is an essential method used in securing data, where the original information, called plaintext, is transformed using an algorithm and an encryption key into a non-readable form called ciphertext. Only individuals with the corresponding decryption key can revert the ciphertext back to its original form, which makes this process a cornerstone of data security in computer systems.