The source is for software delelopers or people who know how to compile the source into the binary.
The source is code written by a programmer in a high-level language and readable by people but not computers. Source code must be converted to object code (aka binary) or machine language before a computer (xbox) can read or execute the program.
So, someone has compiled the sorce into the binary already for you, hence you'll only need the binary.
btw, turn caps lock off, theres no need to shout.