The initial encryption standard developed by NIST was called data encryption standard (DES). DES is too weak for modern applications since the key size is only 56-bit. It was replaced by advanced encryption standard (AES). AES has variable key sizes and can require a key size of 256-bit.

Discuss if you think AES key size has a direct relationship with algorithm strength.
Do you think that AES-256 is necessarily better than AES-128?
How long do you think it would take to launch a brute force attack on AES-128 using a standard computer?