Free Software Foundation (1985)
Open Source Initiative (1998)
Free Software allows users to run it for any purpose and to redistribute copies. Users can study how the program works, make changes, and distribute copies of the new version.
Open Source software is available in source code form for free. Users can view the code and change it to meet their specific needs. It can also be rewritten and distributed as a new program.
Free Software and Open Source have roughly the same aims but differ in philosophy and values. For the former, non-free software is a social problem and free software is the solution. For the latter, proprietary software is a suboptimal solution. Both are fighting the same battle on different fronts.
FOSS is designed to be honest and transparent. Easy access to the source code means that there is nothing intentionally hidden, although a certain degree of technical literacy may be required to read and understand the code.According to the Linux Foundation, if you use software today, at least 80% of it is FOSS.