AES is a subset of the Rijndael family of ciphers. AES includes three members of the Rijndael family, each with a block size of 128 bits but different key lengths of 128, 192 and 256 bits.
AES has been adopted by the United States government and is now used worldwide. It supersedes the Data Encryption Standard (DES). The algorithm described by AES is a symmetric-key algorithm. That is, the same key is used for both encrypting and decrypting the data.
The federal standard document FIPS PUB 197 (FIPS 197) describes this algorithm.