Original: AES has a fixed  block size of 128 bits and a key size of 128, 192, or 256 bits, whereas Rijndael can be specified with block and key sizes in any multiple of 32 bits, with a minimum of 128 bits and a maximum of 256 bits.
Simplified: AES has a fixed block sizes of 128 bits and three values of key size 128, 192, or 256 bits.