AES (Advanced Encryption Standard) is a specification for the encryption of data established by US National Institute of Standards and Technology (NIST) in 2002 as a replacement for the older DES (Data Encryption Standard), which was felt to be susceptible to brute-force attacks. AES is now a worldwide standard.
AES is based on the Rijndael cipher (the name is based on the names of its developers, Joan Daemen and Vincent Rijmen). Rijndael was chosen during a selection process that included a number of different algorithms.
AES is a symmetric-key algorithm: i.e. the same key is used for both encryption and decryption of data.