Free software is software that gives you the user the freedom to share, study and modify it. Free software has become the foundation of a learning society where we share our knowledge in a way that others can build upon and enjoy.
The free software movement was started in 1983 by computer scientist Richard M. Stallman, when he launched a project called GNU, which stands for “GNU is Not UNIX”, to provide a replacement for the UNIX operating system. Then in 1985, Stallman started the Free Software Foundation, a nonprofit organization with the mission of advocating and educating on behalf of computer users around the world.
In 1998, a part of the free software community splintered off and began campaigning in the name of open source. Nearly all open source software is free software. The two terms describe almost the same category of software, but they stand for views based on fundamentally different values.
Open source is a development methodology; free software is a social movement.
Read the statement of Richard Stallman “Why Open Source misses the point of Free Software”.