Steganography is an indirect form of encryption which basically involves hiding messages in files, usually it mixes in with encryption on its own.

http://www.coderprofile.com/source-code/389/bitmap-steganographer

This shows a program I made to hide messages in a bitmap image file.

It works because the first 54 bytes of a Bitmap File are the headers.
Yet, the integer at the offset 10, (10-14), specifies where the bitmap colour data starts.

So, if we modify the offset of the beggining of the bitmap colour data, we can hide messages between the headers and the raw data =]

You can experiement with other file formats using the same principle, just remember that with Hex editing software it is easy to find raw data, encoding it usually does the trick to make it that bit more secure.