You use SHA functions to take a large document and compute a "digest" (also called "hash") of the input. It's important to realize that this is a one-way process. You can't take a digest and recover the original document.
AES, the Advanced Encryption Standard is a symmetric block algorithm. This means that it takes 16-byte blocks and encrypts them. It is "symmetric" because the key allows for both encryption and decryption.
In other words, to conclude, SHA isn't encryption, it's a one-way hash function. AES (Advanced_Encryption_Standard) is a symmetric encryption standard.
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