What is Open Source?

Open Source refers to the fact that the source code of Free Software is open to and for the world to take, to modify and to reuse. The precise meaning of Free Software is spelled out in the Debian Free Software Guidelines or the Free Software Definition while Open Source is defined officially by the Open Source Definition. Open Source and Free Software refer to, originally the same (around Feb 1998), but now different but largely similiar, set of software, but they emphasize different rationals.