When you try to decrypt something using AES_256 or similar, using the wrong decryption
key, the result is cryptographic noise. Cryptographic noise is data that might as well have been randomly generated, as it is not even close to the original, no matter how similar the decryption key you put in is to the correct decryption key. This is as a result of the strong diffusion and confusion principles employed by modern encryption standards
like AES-256. Even if youre only slightly off from the correct decryption key, say you forgot to capitalise a letter, you
will never get a "partially correct" or "degraded" version of the original data. It
will generate what one might describe as "corrupted, meaningless garbage, taking up space on your
computer."