What is steganography?
Background
Are you interested in cryptography?
Steganography tied tightly with cryptography but a little different from it. The difference is that whether the encryption process is opened to others. While hiding information by encryption, the information hided is unknown to others, but the hiding process is known by others, with steganography not known by others.
Why steganography?
Steganography is a technology for hiding secret information in common files. It's better than just encrypt secret information as others even don't know you have secret to be hidden.
How steganography?
There are lots of powerful tools for steganography such as Steghide and Stegosuite. Have a try of them.