In encryption technology, what does the term "cipher" refer to?

The term "cipher" specifically refers to a method or algorithm that is used for encrypting and decrypting data. It provides a systematic way to transform plaintext into ciphertext, making the information secure from unauthorized access. Ciphers can vary widely in complexity and structure, ranging from simple substitution or transposition techniques to more advanced algorithms like AES or RSA. The primary function of a cipher is to ensure that sensitive information remains confidential and can only be read or processed by individuals or systems that possess the appropriate decryption key. This definition is crucial for understanding how encrypted communication and data protection work in practice.