Apart from something you should do after every meal, FLOSS stands for Free/Libre & Open Source Software. GNU/Linux is FLOSS. What does this mean?
The Free Software Foundation says:
“Free software” means software that respects users' freedom and community. Roughly, it means that the users have the freedom to run, copy, distribute, study, change and improve the software. Thus, “free software” is a matter of liberty, not price. To understand the concept, you should think of “free” as in “free speech,” not as in “free beer”.
The Open Source Initiative says:
Open source software is software that can be freely used, changed, and shared (in modified or unmodified form) by anyone. Open source software is made by many people, and distributed under licenses that comply with the Open Source Definition.
If you are curious as to the differences between these two terms, I suggest you read this.
What are other examples of FLOSS?
Mozilla Firefox, LibreOffice and VLC are examples of other prominent FLOSS. See our Software Guide for more examples.
Is everything that runs on GNU/Linux free and open-source software?
No. Companies and individuals can make proprietary non-free and non-open-source software that runs on GNU/Linux. Although some people are ideologically opposed to this, and free and open-source software is preferable to proprietary software, this is yet another option open to GNU/Linux programmers and users.