Free and Open Source Software (sometimes called Open Source or FLOSS, and referred to in this paper by the commonly used term FOSS) is an approach to software that emphasizes the freedoms provided to end users. Originally formulated in 1983 by a computer scientist concerned with access to technology, it has become a central component of mainstream IT. The popularity of FOSS has produced a wealth of related terminology and perspectives which occasionally lead to confusion about what it actually is and what are the best ways to engage with the field. This paper will address such confusion by providing a clear overview of FOSS, how it works, and why it is successful. It will go back to first principles in defining FOSS, explaining the concept of licensing that underpins it, and examining how this paradigm facilitates multiple development and business models. The key assertion is that the productive application of FOSS relies on good governance model ( or models) may be best suited to the long-term sustenance of FOSS as an approach to developing knowledge products, the indicators provided by the previous two decades suggest that FOSS governance will continue to be effectively refined by its stakeholders.