A coded message is a form of communication that uses a code or CIPHER to conceal the meaning of the message. A CIPHER is a type of code in which each letter of the original message is replaced with another letter or symbol, while a CRYPTOGRAM is a type of code in which each letter of the original message is replaced with a different letter or symbol. Both ciphers and cryptograms are used to create coded messages that can only be decoded by those who know the code.