In cryptography, a cryptosystem is a suite of cryptographic algorithms needed to implement a particular security service, such as confidentiality (encryption).
[1] Typically, a cryptosystem consists of three algorithms: one for key generation, one for encryption, and one for decryption.
The term cipher (sometimes cypher) is often used to refer to a pair of algorithms, one for encryption and one for decryption.
Therefore, the term cryptosystem is most often used when the key generation algorithm is important.
[2] Note; typically this definition is modified in order to distinguish an encryption scheme as being either a symmetric-key or public-key type of cryptosystem.
AES is a widely used symmetric encryption algorithm that has become the standard for securing data in various applications.
Paillier cryptosystem is another example used to preserve and maintain privacy and sensitive information.