Free and open source software (in short, FOSS) is software that is distributed in a manner that allows its users to run the software for any purpose, to redistribute copies of, and to examine, study, and modify, the source code. FOSS is also a loosely associated movement of multiple organizations, foundations, communities and individuals who share basic philosophical perspectives and collaborate practically, but might diverge in detail questions.
Historical precursor is the hobbyist and academic public domain software ecosystem of the 1960s to 1980s. The FOSS movement's "free" part originates from Richard Matthew Stallman who noted the lost freedom to users on the decline of the public domain ecosystem and the grow of a copyright'ed proprietary software ecosystem. As response, he created as hack of the copyright system the GPL, a protective license, aiming for the creation of a complete and free operating system — GNU. Shortly after the BSDs (FreeBSD, OpenBSD, NetBSD) brought an alternative FOSS approach on the table, the more public domain like permissive licenses and its ecosystem. Other noteworthy FOSS organizations from this time include the Apache Foundation (Apache Server), GNOME, Debian, Mozilla Foundation (Firefox), with their own ideas: The Free Software Definition, Debian Free Software Guidelines, The Open Source Definition and more. On end of 1990s, in context of the dot-com bubble and web 2.0, the Open Source movement (with Eric S. Raymond, Bruce Perens, Tim O'Reilly and others) gave important impulses to FOSS with the achieved open sourcing of Netscape's browser as Firefox and Sun Microsystems' office suit as OpenOffice.org. The rise of Linus Torvalds' Linux as general purpose OS in the 2000s finally paved the way to broad mainstream recognition and acceptance of FOSS in the IT domain and general public. In the 2010s GitHub's openness and collaboration encouraging software repository cloud service brought FOSS software development & maintenance methodologies to mainstream software development.
The FOSS movement gave inspiration on the creation of many related movements, like the Open access, Open hardware, Open content, Free culture, open standards and many more.