Steganography is the study and practice of concealing information within objects in such a way that it deceives the viewer as if there is no information hidden within the object. Simply put, it is hiding information in plain sight, such that only the intended recipient would get to see it.
It may immediately occur to us that this is similar to cryptography, but it is not so. In cryptography, the objective is to modify the original message in such a fashion it becomes difficult to get to the original message from the modified message. The original and modified messages are explicitly expected to look different. While in image steganography, the objective is to deceptively hide a message within another original message and thereby, modifying it. The modified message is expected to look very similar to the original message.
Prime objective is to share messages or information discreetly
Hackers using steganography techniques for malware transmission
Intelligence agencies use them for communication.