This is unfortunately not really the right forum to ask general questions about encryption.
The key is the key used to encrypt, i.e. “password” in very non-technical terms.
The block is the unit of data that is passed through the algorithm, for AES this is 128 bits, or 16 bytes.
I suggest you read the Wikipedia page on AES, https://en.wikipedia.org/wiki/Advanced_Encryption_Standard .