This is computer language. Each character you see on this screen has a binary number code that tells the computer to translate it into the character you see. Each character consist of 8 bits. Each of the 8 bit numbers can be either a 1 or a 0. This is the smallest fragment of the logistics of computer language. For example:
What you see "D"
What the computer sees "01000100"
http://asciitable.com has the table of how this works and what other character codes are.
What is binary?
