For example (again over simplified): If a message is encrypted using substitution (substituting one alphabet with another), permute the message (shuffle the text) and apply a substitution again, then the encrypted ciphertext is more secure than using only substitution or only permutation. NOW, if the ciphertext is embedded in an [image, video, voice, etc.] it is even more secure. If an encrypted message is intercepted, the interceptor knows the text is an encrypted message. With steganography, the interceptor may not know the object contains a message.